Downtown Los Angeles (USC) has ended the 2017-18 rain
year (July 1 to June 30) with only 4.79 inches of rain. That makes 2017-18 the third
driest rain year since recordkeeping began in July 1877. The rainfall total was
only 32% of normal and is less rain than was recorded during any rain year in our
recent five year drought. The three driest rain years in Los Angeles have all occurred
since 2001.

The June
2018 EL NIÑO/SOUTHERN OSCILLATION (ENSO) DIAGNOSTIC DISCUSSION says El Nino conditions
are favored to develop during the Northern Hemisphere fall, and and this is the most
likely ENSO state to be present this winter. According to the CPC/IRI consensus forecast
there is a 50% chance of El Nino conditions developing this fall, with the probability
increasing to about 65% this winter.

Keeping in mind last year's "failed" El Nino, the April-May
value of the Multivariate
ENSO Index (MEI) increased 0.9 SD to 0.47. This is just below the threshold of
a weak El Niño ranking. Klaus Wolter's empirical analysis using historical analogues
suggests that, compared to last month, the odds for the development of El Niño conditions
later this year have dramatically increased.

If Los Angeles rain year precipitation is averaged for
El Nino episodes (CPC
ERSSTv5) since 1950, the average is about 120% of normal. However, El Nino conditions
do not guarantee above average rainfall, particularly in the last 15 years or so.
The driest rain year on record in Los Angeles (2006-07) was during an El Nino; and
two rain years (2014-15 & 2015-16) of our recent five year drought were during
an El Nino.

More information about Southern California weather and
climate can be found using our WEATHER LINKS page.

Southern California Weather Notes Copyright 2000-2017 Gary Valle. All Rights Reserved.
Third Driest Rain Year on Record for Downtown Los Angeles. Forecasts Says Better than 50/50 Chance of El Nino Developing Later This Year.http://www.sierraphotography.com/wxnotes/PermaLink,guid,304eedb1-0424-43e8-bf20-7aa26f2bfb94.aspxhttp://www.sierraphotography.com/wxnotes/ThirdDriestRainYearOnRecordForDowntownLosAngelesForecastsSaysBetterThan5050ChanceOfElNinoDevelopingLaterThisYear.aspx
Mon, 02 Jul 2018 17:58:36 GMT
<div id="mainwx">
<div class="fltrt">
<p align="center">
<a href="wxdata1819/sst_mean_anom_201607_201807_2018070114b.jpg" title="TAO/TRITON Five-Day SST - TAO/TRITON Five-Day SST - July 2016 to June 2018" target="_blank" rel="wximage"> <img src="wxdata1819/sst_mean_anom_201607_201807_2018070114c.jpg" alt="TAO/TRITON Five-Day SST - July 2016 to June 2018" width="350" height="252" border="0" /> </a> <img alt="Click" src="http://www.sierraphotography.com/wxnotes/images/click.gif" width="16" height="34" />
<br />
<span class="fontxxsmall">TAO/TRITON Five-Day SST<br />
July 2016 to June 2018</span>
</p>
</div>
<p>
<span class="dropcap">D</span>owntown Los Angeles (USC) has ended the 2017-18 rain
year (July 1 to June 30) with only 4.79 inches of rain. That makes 2017-18 the <a href="wxdata1718/SC_ACIS2_KCQT_RY_063018.png" target="_blank" rel="wximage">third
driest rain year</a> since recordkeeping began in July 1877. The rainfall total was
only 32% of normal and is less rain than was recorded during any rain year in our
recent five year drought. The three driest rain years in Los Angeles have all occurred
since 2001.
</p>
<p>
<span class="dropcap">T</span>he <a href="EL NIÑO/SOUTHERN OSCILLATION (ENSO)" target="_blank">June
2018 EL NIÑO/SOUTHERN OSCILLATION (ENSO) DIAGNOSTIC DISCUSSION</a> says El Nino conditions
are favored to develop during the Northern Hemisphere fall, and and this is the most
likely ENSO state to be present this winter. According to the CPC/IRI consensus forecast
there is a 50% chance of El Nino conditions developing this fall, with the probability
increasing to about 65% this winter.
</p>
<p>
<span class="dropcap">K</span>eeping in mind last year's "failed" El Nino, the April-May
value of the <a href="https://www.esrl.noaa.gov/psd/enso/mei/index.html" target="_blank">Multivariate
ENSO Index</a> (MEI) increased 0.9 SD to 0.47. This is just below the threshold of
a weak El Niño ranking. Klaus Wolter's empirical analysis using historical analogues
suggests that, compared to last month, the odds for the development of El Niño conditions
later this year have dramatically increased.
</p>
<p>
<span class="dropcap">I</span>f Los Angeles rain year precipitation is averaged for
El Nino episodes (<a href="http://origin.cpc.ncep.noaa.gov/products/analysis_monitoring/ensostuff/ONI_v5.php" target="_blank">CPC
ERSSTv5</a>) since 1950, the average is about 120% of normal. However, El Nino conditions
do not guarantee above average rainfall, particularly in the last 15 years or so.
The driest rain year on record in Los Angeles (2006-07) was during an El Nino; and
two rain years (2014-15 &amp; 2015-16) of our recent five year drought were during
an El Nino.
</p>
<p>
<span class="dropcap">M</span>ore information about Southern California weather and
climate can be found using our <a href="weatherlinks.htm">WEATHER LINKS</a> page.
</p>
</div>
<img width="0" height="0" src="http://www.sierraphotography.com/wxnotes/aggbug.ashx?id=304eedb1-0424-43e8-bf20-7aa26f2bfb94" />
<br />
<hr />Southern California Weather Notes Copyright 2000-2017 Gary Valle. All Rights Reserved.climatedroughtEl NinoLos Angeles rainfallMultivariate ENSO Index (MEI)http://www.sierraphotography.com/wxnotes/Trackback.aspx?guid=42541869-964a-446a-bbe2-1e7b8739fc59http://www.sierraphotography.com/wxnotes/pingback.aspxhttp://www.sierraphotography.com/wxnotes/PermaLink,guid,42541869-964a-446a-bbe2-1e7b8739fc59.aspxGary Valle

The following chart compares various climate parameters
for cold ENSO episodes that have occurred since 1949. Except where noted the cold
episodes listed are those specified in the CPC's tabulation of Cold & Warm Episodes
by Season. The cold and warm episodes are based on the Oceanic Niño Index (ONI), which
is calculated using the three month running mean of ERSST.v5 SST anomalies in the
Niño 3.4 region with multiple-centered 30 year base periods. A description of the
parameters follows the chart. With the exception of years prior to 1957, a Nov-Mar
GWO phase space plot is included for each episode. Data for 2017-18 will be updated
periodically.

Year

ERSST
Version

Nov-Mar
AAM

Peak MEI4

Peak MEI Season

Peak
ONI

Peak ONI Season

L.A. Rain

GWO
Phase Plot

1949-501,2

v5

--

-1.445

APRMAY

-1.5

DJF

9.94

--

1950-511,3

v4

--

-1.235

NOVDEC

-0.8

NDJ, DJF

8.21

--

1954-551

v5

--

-1.528

MAYJUN (54)

-0.9

ASO

11.94

--

1955-561

v5

--

-2.209

MAYJUN (55)

-1.7

OND

16.00

--

1956-571

v3b

--

-1.490

MAYJUN (56)

-0.4

Several

9.54

--

1961-62

v2

-0.515

-1.065

DECJAN

-0.3

ASO, SON

18.79

1962-63

v3b

-1.264

-0.837

JANFEB

-0.4

OND, NDJ

8.38

1964-65

v5

-1.150

-1.476

JULAUG

-0.8

ASO - DJF

13.69

1967-683

v4

-0.773

-1.106

APRMAY

-0.7

JFM

16.58

1970-71

v5

-0.980

-1.870

MARAPR

-1.4

DJF, JFM

12.32

1971-72

v5

-0.174

-1.439

AUGSEP

-1.0

OND

7.17

1973-74

v5

-1.336

-1.912

DECJAN

-2.0

NDJ

14.92

1974-75

v5

-0.846

-1.230

OCTNOV

-0.8

OND

14.35

1975-76

v5

-0.716

-1.968

SEPOCT

-1.7

OND, NDJ

7.22

1983-84

v5

-1.099

-0.509

JANFEB

-1.0

OND

10.43

1984-85

v5

-0.600

-0.715

APRMAY

-1.1

NDJ

12.82

1988-89

v5

-1.144

-1.501

AUGSEP

-1.8

OND, NDJ

8.08

1995-96

v5

-0.227

-0.597

DECJAN

-1.0

SON - NDJ

12.46

1998-99

v5

-0.544

-1.123

JANFEB

-1.6

NDJ, DJF

9.09

1999-00

v5

-0.784

-1.189

JANFEB

-1.7

NDJ, DJF

11.57

2000-01

v5

-0.801

-.701

OCTNOV

-0.7

OND - DJF

17.94

2005-06

v5

-0.616

-0.575

MARAPR

-0.8

NDJ, DJF

13.19

2007-08

v5

-1.015

-1.579

FEBMAR

-1.6

NDJ - DJF

13.53

2008-09

v5

-0.599

-.723

FEBMAR

-0.8

DJF

9.08

2010-11

v5

-0.598

-1.888

AUGSEP

-1.7

SON, OND

20.20

2011-12

v5

-0.371

-0.980

DECJAN

-1.1

SON, OND

8.69

2016-17

v5

0.088

-0.363

SEPOCT

-0.7

ASO - OND

19.00

2017-185

v5

-0.550

-0.731

JANFEB

-1.0

NDJ

4.68

1. AAM and AAM tendency anomaly data not available.
2. Based on ONI values beginning with DJF 1949-50.
3. ONI did not meet threshold of 5 consecutive overlapping seasons using ERSST v5.
4. MEI values are normalized and may change as new data is added. Specified values
were current as of March 6, 2018.
5. Data as of March 31, 2018.

ERSST Version: The most recent ERSST version for which the
episode was designated a cold episode. (See Peak ONI below.)

Nov-Mar AAM: The mean of the global relative atmospheric angular
momentum anomaly for the period November 1 to March 31 of the following year. GWO
phase space data is calculated using code from the Global
Synoptic Dynamic Model page of the PSD Map Room Climate Products. Reference Weickmann
and Berry, 2008.

Downtown Los Angeles (USC) finished the 2016-17 rainfall
year (July 1 to June 30) with 19.00 inches of recorded precipitation. This is about
127% of the 1981-2010 normal of 14.93 inches. This was the first rain year with above
normal precipitation at Los Angeles since 2009-2010, when 20.2 inches was recorded.

As of May 2017 the Pacific
Decadal Oscillation Index has been positive (warm) since January 2014 -- a record
41 consecutive months. The previous record streak was 36 months, from August 1991
to July 1994.

Most climate outlooks are projecting ENSO Neutral conditions
are favored to persist into the Northern Hemisphere fall, with a lesser chance of
weak El Nino conditions developing over that period. Perhaps supporting the notion
of El Nino development, the April-May value of the Multivariate
ENSO Index (MEI) increased by 0.69 standard deviations from 0.77 to 1.46. This
is solidly within the index's El Nino ranking and at the threshold of a strong El
Niño ranking. According to Klaus Wolter, the increase over the last three months is
the second largest on record for this time of year, exceeded only by 1997. We'll see
if ENSO conditions remain neutral or some form of ENSO warming (Central Pacific?)
takes place.

More information about Southern California weather and
climate can be found using our WEATHER LINKS page.

Southern California Weather Notes Copyright 2000-2017 Gary Valle. All Rights Reserved.
Downtown Los Angeles Ends Rainfall Year at 127% of Normal. Record PDO Positive Streak. MEI Near Strong El Nino Threshold.http://www.sierraphotography.com/wxnotes/PermaLink,guid,cdc254c6-61ff-4911-ad49-663314706bc3.aspxhttp://www.sierraphotography.com/wxnotes/DowntownLosAngelesEndsRainfallYearAt127OfNormalRecordPDOPositiveStreakMEINearStrongElNinoThreshold.aspx
Sat, 01 Jul 2017 01:44:36 GMT
<div id="mainwx">
<div class="fltrt">
<p align="center">
<a href="wxdata1617/time_lon_EQ_hf_sst_sst_mean_anom_201506_201706_2017063014b.jpg" title="TAO/TRITON Five-Day SST - June 2015 to June 2017" target="_blank" rel="wximage"> <img src="wxdata1617/time_lon_EQ_hf_sst_sst_mean_anom_201506_201706_2017063014c.jpg" alt="TAO/TRITON Five-Day SST - June 2015 to June 2017" width="350" height="252" border="0" /> </a> <img alt="Click" src="http://www.sierraphotography.com/wxnotes/images/click.gif" width="16" height="34" />
<br />
<span class="fontxxsmall">TAO/TRITON Five-Day SST<br />
June 2015 to June 2017</span>
</p>
</div>
<p>
<span class="dropcap">D</span>owntown Los Angeles (USC) finished the 2016-17 rainfall
year (July 1 to June 30) with 19.00 inches of recorded precipitation. This is about
127% of the 1981-2010 normal of 14.93 inches. This was the first rain year with above
normal precipitation at Los Angeles since 2009-2010, when 20.2 inches was recorded.
</p>
<p>
<span class="dropcap">A</span>s of May 2017 the <a href="http://research.jisao.washington.edu/pdo/" target="_blank">Pacific
Decadal Oscillation Index</a> has been positive (warm) since January 2014 -- a record
41 consecutive months. The previous record streak was 36 months, from August 1991
to July 1994.
</p>
<p>
<span class="dropcap">M</span>ost climate outlooks are projecting ENSO Neutral conditions
are favored to persist into the Northern Hemisphere fall, with a lesser chance of
weak El Nino conditions developing over that period. Perhaps supporting the notion
of El Nino development, the April-May value of the <a href="https://www.esrl.noaa.gov/psd/enso/mei/index.html" target="_blank">Multivariate
ENSO Index</a> (MEI) increased by 0.69 standard deviations from 0.77 to 1.46. This
is solidly within the index's El Nino ranking and at the threshold of a strong El
Niño ranking. According to Klaus Wolter, the increase over the last three months is
the second largest on record for this time of year, exceeded only by 1997. We'll see
if ENSO conditions remain neutral or some form of ENSO warming (Central Pacific?)
takes place.
</p>
<p>
<span class="dropcap">M</span>ore information about Southern California weather and
climate can be found using our <a href="weatherlinks.htm">WEATHER LINKS</a> page.
</p>
</div>
<img width="0" height="0" src="http://www.sierraphotography.com/wxnotes/aggbug.ashx?id=cdc254c6-61ff-4911-ad49-663314706bc3" />
<br />
<hr />Southern California Weather Notes Copyright 2000-2017 Gary Valle. All Rights Reserved.climateEl NinoLos Angeles rainfallMultivariate ENSO Index (MEI)weatherhttp://www.sierraphotography.com/wxnotes/Trackback.aspx?guid=848bda88-7ae8-4b30-a90c-764632b6f2d4http://www.sierraphotography.com/wxnotes/pingback.aspxhttp://www.sierraphotography.com/wxnotes/PermaLink,guid,848bda88-7ae8-4b30-a90c-764632b6f2d4.aspxGary Valle

California Percent of Normal Precipitation (WRCC)
July 1, 2016 to January 22, 2017

Update on February 2, 2017. Downtown Los Angeles has ended January 2017 with
8.38 inches of rain. This is 269% of the normal January rainfall total of 3.12 inches.
The preliminary Rain Year precipitation total for Downtown Los Angeles for July 1
through January 31, 2017 is 14.33 inches, which is 193% of the normal amount of 7.44
inches. Here is an updated California
Percent of Normal Precipitation map from the Western Regional Climate Center for
July 1, 2016 to January 31, 2017.

On the heels of a wet December, a series of Pacific storms
have resulted in the wettest start to the Rain Year (July 1 - June 30) and Water Year
(October 1 to September 30) since the very wet year of 2004-2005.

The last
system of the series, which brought very heavy precipitation to the area on Sunday,
was associated with a well-defined
atmospheric river. Precipitation totals in the Los Angeles area for the storm
generally ranged from about 2 to 5 inches. According to the NWS, new rainfall records
for January 23 were set at Los Angeles Airport (2.94 inches), Camarillo (2.74 inches)
and Long Beach Airport (3.97 inches). The rainfall at Long Beach Airport was the most
ever recorded in a day at that location. Here are some precipitation totals from around
the area compiled by the NWS
Los Angeles/Oxnard and NWS
San Diego.

As of yesterday Downtown Los Angeles (USC) has recorded
14.33 inches of rain for the Rain Year. This is 217% of the normal amount of 6.65
inches for the date, and 97% of the normal amount of rainfall for an entire year.
Assuming we don't get any more rain this January, the 8.38 inches recorded will work
out to 269% of the normal amount for the month.

A little precipitation has crept back into the GFS, GEFS
and ECMWF forecasts for the Los Angeles area the first week of February. We'll see!

More information about Southern California weather and
climate can be found using our WEATHER LINKS page.

Southern California Weather Notes Copyright 2000-2017 Gary Valle. All Rights Reserved.
Wettest Start to the Rain Year for Los Angeles Since 2004-2005. Rain Year Precipitation Above Normal for Most of California.http://www.sierraphotography.com/wxnotes/PermaLink,guid,848bda88-7ae8-4b30-a90c-764632b6f2d4.aspxhttp://www.sierraphotography.com/wxnotes/WettestStartToTheRainYearForLosAngelesSince20042005RainYearPrecipitationAboveNormalForMostOfCalifornia.aspx
Wed, 25 Jan 2017 03:10:12 GMT
<div id="mainwx">
<div class="fltrt">
<p align="center">
<a href="wxdata1617/WRCC_PoN_CA_070116_012217b.gif" title="California Percent of Normal Precipitation for July 1 to January 22, 2017 (WRCC)" target="_blank" rel="wximage"> <img src="wxdata1617/WRCC_PoN_CA_070116_012217c.gif" alt="California Percent of Normal Precipitation for July 1 to January 22, 2017 (WRCC)" width="193" height="250" border="0" /> </a> <img alt="Click" src="http://www.sierraphotography.com/wxnotes/images/click.gif" width="16" height="34" />
<br />
<span class="fontxxsmall">California Percent of Normal Precipitation (WRCC)<br />
July 1, 2016 to January 22, 2017</span>
</p>
</div>
<p>
<i>Update on February 2, 2017</i>. Downtown Los Angeles has ended January 2017 with
8.38 inches of rain. This is 269% of the normal January rainfall total of 3.12 inches.
The preliminary Rain Year precipitation total for Downtown Los Angeles for July 1
through January 31, 2017 is 14.33 inches, which is 193% of the normal amount of 7.44
inches. Here is an updated <a href="wxdata1617/WRCC_PoN_CA_070116_013117b.gif" rel="wximage">California
Percent of Normal Precipitation map</a> from the Western Regional Climate Center for
July 1, 2016 to January 31, 2017.
</p>
<p>
<span class="dropcap">O</span>n the heels of a wet December, a series of Pacific storms
have resulted in the wettest start to the Rain Year (July 1 - June 30) and Water Year
(October 1 to September 30) since the very wet year of 2004-2005.
</p>
<p>
<span class="dropcap">T</span>he six day period from January 18-23 was particularly
wet, with three storms producing a total of 5.53 inches of rain at Downtown Los Angeles
(USC). Here are some <a href="wxdata1617/VCWPD_PrecipMap_7Day_012417_0700d.jpg" target="_blank" rel="wximage">preliminary
7-day precipitation totals from around the area</a> from the Ventura County Watershed
Protection District.
</p>
<p>
<span class="dropcap">T</span>he <a href="wxdata1617/uwmad_goeswestwv_012217_1530zb.jpg" target="_blank" rel="wximage">last
system of the series</a>, which brought very heavy precipitation to the area on Sunday,
was associated with a <a href="wxdata1617/NESDIS_CONUS_TPW_20170122_23Z.png" target="_blank" rel="wximage">well-defined
atmospheric river</a>. Precipitation totals in the Los Angeles area for the storm
generally ranged from about 2 to 5 inches. According to the NWS, new rainfall records
for January 23 were set at Los Angeles Airport (2.94 inches), Camarillo (2.74 inches)
and Long Beach Airport (3.97 inches). The rainfall at Long Beach Airport was the most
ever recorded in a day at that location. Here are some precipitation totals from around
the area compiled by the <a href="wxdata1617/RRMLOX012417_0638PST.pdf" target="_blank">NWS
Los Angeles/Oxnard</a> and <a href="wxdata1617/RRMSGX012417_0403PST.pdf" target="_blank">NWS
San Diego</a>.
</p>
<p>
<span class="dropcap">A</span>s of yesterday Downtown Los Angeles (USC) has recorded
14.33 inches of rain for the Rain Year. This is 217% of the normal amount of 6.65
inches for the date, and 97% of the normal amount of rainfall for an entire year.
Assuming we don't get any more rain this January, the 8.38 inches recorded will work
out to 269% of the normal amount for the month.
</p>
<p>
<span class="dropcap">T</span>he California Cooperative Snow Surveys <a href="http://cdec.water.ca.gov/cgi-progs/reports/DLYSWEQ.20170124" target="_blank">Snow
Water Equivalents report for today</a> puts the snowpack for the date at an average
197% of normal. That's two times the normal amount.
</p>
<p>
<span class="dropcap">A</span> little precipitation has crept back into the GFS, GEFS
and ECMWF forecasts for the Los Angeles area the first week of February. We'll see!
</p>
<p>
<span class="dropcap">M</span>ore information about Southern California weather and
climate can be found using our <a href="weatherlinks.htm">WEATHER LINKS</a> page.
</p>
</div>
<img width="0" height="0" src="http://www.sierraphotography.com/wxnotes/aggbug.ashx?id=848bda88-7ae8-4b30-a90c-764632b6f2d4" />
<br />
<hr />Southern California Weather Notes Copyright 2000-2017 Gary Valle. All Rights Reserved.droughtLos Angeles rainfallrecord rainfallSierra snowpackweatherhttp://www.sierraphotography.com/wxnotes/Trackback.aspx?guid=28bee348-2f64-4738-8a77-cd0e58a0edd4http://www.sierraphotography.com/wxnotes/pingback.aspxhttp://www.sierraphotography.com/wxnotes/PermaLink,guid,28bee348-2f64-4738-8a77-cd0e58a0edd4.aspxGary Valle

California Percent of Normal Precipitation (WRCC)
July 1, 2016 to December 26, 2016

As of today Downtown Los Angeles (USC) December rainfall
is 1.75 inches above the monthly normal of 2.33 inches. Not since the beginning of
the drought has Los Angeles experienced such a wet December. The 4.08 inches of rain
recorded so far this month is the most since December 2010 and the most for any month
since January 2010.

Since the Rain Year began July 1, 5.48 inches of rain
has fallen at Downtown Los Angeles (USC). This is more than an inch above the normal
July-December rainfall of 4.32 inches. It is the best start to the Rain Year (Jul
1-Jun 30) and Water Year (Oct 1-Sep 30) since 2010.

Forecasting how the cut off upper level low currently
spinning offshore southwest of Los Angeles and a developing upstream trough interact
is a tough task, even for a supercomputer. The trough is expected to propel the low
in our general direction and then replace/absorb it. Add to the mix the possibility
of pulling up some sub-tropical moisture (or not) and the forecast becomes even trickier.
Guess we'll see!

More information about Southern California weather and
climate can be found using our WEATHER LINKS page.

Southern California Weather Notes Copyright 2000-2017 Gary Valle. All Rights Reserved.
Downtown Los Angeles Rainfall Above Normal. Cut Off Upper Low Waits Offshore.http://www.sierraphotography.com/wxnotes/PermaLink,guid,28bee348-2f64-4738-8a77-cd0e58a0edd4.aspxhttp://www.sierraphotography.com/wxnotes/DowntownLosAngelesRainfallAboveNormalCutOffUpperLowWaitsOffshore.aspx
Tue, 27 Dec 2016 23:50:30 GMT
<div id="mainwx">
<div class="fltrt">
<p align="center">
<a href="wxdata1617/WRCC_PoN_CA_070116_122616b.gif" title="California Percent of Normal Precipitation for July 1 to December 26, 2016 (WRCC)" target="_blank" rel="wximage"> <img src="wxdata1617/WRCC_PoN_CA_070116_122616c.gif" alt="California Percent of Normal Precipitation for July 1 to December 26, 2016 (WRCC)" width="193" height="250" border="0" /> </a> <img alt="Click" src="http://www.sierraphotography.com/wxnotes/images/click.gif" width="16" height="34" />
<br />
<span class="fontxxsmall">California Percent of Normal Precipitation (WRCC)<br />
July 1, 2016 to December 26, 2016</span>
</p>
</div>
<p>
<span class="dropcap">A</span>s of today Downtown Los Angeles (USC) December rainfall
is 1.75 inches above the monthly normal of 2.33 inches. Not since the beginning of
the drought has Los Angeles experienced such a wet December. The 4.08 inches of rain
recorded so far this month is the most since December 2010 and the most for any month
since January 2010.
</p>
<p>
<span class="dropcap">S</span>ince the Rain Year began July 1, 5.48 inches of rain
has fallen at Downtown Los Angeles (USC). This is more than an inch above the normal
July-December rainfall of 4.32 inches. It is the best start to the Rain Year (Jul
1-Jun 30) and Water Year (Oct 1-Sep 30) since 2010.
</p>
<p>
<span class="dropcap">W</span>hile the rain is good news, this <a href="wxdata1617/WRCC_PoN_CA_070116_122616b.gif" target="_blank" rel="wximage">graphic
from the Western Regional Climate Center</a> shows that the Jul-Dec precipitation
in some areas of Southern California is still below normal.
</p>
<p>
<span class="dropcap">F</span>orecasting how the cut off upper level low <a href="wxdata1617/uwmad_goeswestwv_122716_2130zb.jpg" target="_blank" rel="wximage">currently
spinning offshore</a> southwest of Los Angeles and a developing upstream trough interact
is a tough task, even for a supercomputer. The trough is expected to propel the low
in our general direction and then replace/absorb it. Add to the mix the possibility
of pulling up some sub-tropical moisture (or not) and the forecast becomes even trickier.
Guess we'll see!
</p>
<p>
<span class="dropcap">M</span>ore information about Southern California weather and
climate can be found using our <a href="weatherlinks.htm">WEATHER LINKS</a> page.
</p>
</div>
<img width="0" height="0" src="http://www.sierraphotography.com/wxnotes/aggbug.ashx?id=28bee348-2f64-4738-8a77-cd0e58a0edd4" />
<br />
<hr />Southern California Weather Notes Copyright 2000-2017 Gary Valle. All Rights Reserved.droughtLos Angeles rainfallprecipitation outlookweatherhttp://www.sierraphotography.com/wxnotes/Trackback.aspx?guid=b79e8687-695c-4ba9-939b-a93560e5f047http://www.sierraphotography.com/wxnotes/pingback.aspxhttp://www.sierraphotography.com/wxnotes/PermaLink,guid,b79e8687-695c-4ba9-939b-a93560e5f047.aspxGary Valle

Dead and Dying Coast Redwoods Along Century Lake
Malibu Creek State Park

Downtown Los Angeles (USC) finished the 2015-16 rainfall
year (July 1 to June 30) with 9.65 inches of recorded precipitation. This is about
65% of the 1981-2010 normal of 14.93 inches. This was the fifth consecutive year of
below normal rainfall for Downtown Los Angeles, with a cumulative rainfall deficit
of 35.86 inches --nearly three feet!

Observable impacts of the drought are widespread. Trees
have been particularly hard hit. Dead trees can be seen along city streets, in parks,
and throughout the open space areas and wildlands of Southern California. The dead
and dying 100+ year old coast redwoods at Malibu Creek State Park are an example.

Most climate outlooks are forecasting La Nina conditions
to develop over the Northern Hemisphere summer. Historically La Ninas have "on average" resulted
in below normal precipitation in Southern California. But historical composites
can be misleading. During the last five La Nina episodes (1999-00, 2000-01, 2007-08,
2010-11, 2011-12) Downtown Los Angeles (USC) has averaged 14.39 inches of rain, which
is 96% of normal.

Even during one of three strongest El Ninos on record,
precipitation outlooks based on historical composites and analogs didn't perform well
in Southern California. Given the somewhat more variable rainfall in Southern California
during La Ninas, to determine the winter precipitation outlook you might as well flip
a three-sided coin.

More information about Southern California weather and
climate can be found using our WEATHER LINKS page.

Following is a chart comparing the 2015-16 El Nino to
warm ENSO episodes that have occurred since 1950. The warm episodes are based on the
revised Oceanic Niño Index (ONI) which is calculated using the three month running
mean of ERSST.v4 SST anomalies in the Niño 3.4 region with multiple-centered 30 year
base periods. Unless noted the warm episodes are those specified in the CPC's tabulation
of Cold & Warm Episodes by Season. A description of the parameters follows the
chart. With the exception of years prior to 1957, a Nov-Mar GWO phase space plot is
included for each warm episode.

Year

Jul-Sep
AAM

Nov-Mar
AAM

Peak MEI

Peak MEI Season

Peak
ONI

Peak ONI Season

L.A. Rain

GWO
Phase Plot

1951-521

--

--

0.822

JULAUG

0.9

SON

26.21

--

1952-532

--

--

0.788

APRMAY

0.7

FMA-AMJ

9.46

--

1953-542

--

--

0.484

AUGSEP

0.8

ASO, SON, OND

11.99

--

1957-583

--

0.773

1.474

DECJAN, JANFEB

1.7

DJF

21.13

1958-59

-0.919

-0.206

0.788

JANFEB

0.6

NDJ, DJF, JFM

5.58

1963-64

0.005

0.046

0.867

OCTNOV, DECJAN

1.2

SON, OND

7.93

1965-66

-0.826

-0.748

1.436

JULAUG

1.8

OND

20.44

1968-69

0.130

0.513

0.844

JANFEB

1.0

JFM

27.47

1969-70

0.358

0.413

0.670

OCTNOV

0.8

ASO, SON, OND

7.77

1972-73

-0.096

-0.239

1.827

JUNJUL, JULAUG

2.0

OND

21.26

1976-77

0.284

-0.828

1.029

AUGSEP

0.8

OND,NDJ

12.31

1977-78

-0.646

1.008

0.993

SEPOCT, OCTNOV

0.8

OND, NDJ

33.44

1979-804

0.496

-0.013

0.996

NOVDEC

0.6

NDJ, DJF

26.98

1982-83

0.938

2.337

3.011

FEBMAR

2.1

OND,NDJ, DJF

31.25

1986-875

0.232

0.019

2.140

APRMAY87

1.2

JFM

7.66

1987-885

1.153

1.000

1.982

JULAUG

1.6

JAS, ASO

12.48

1991-92

-0.008

0.808

2.269

MARAPR

1.6

DJF

21.00

1994-95

-0.422

0.764

1.419

SEPOCT

1.0

NDJ

24.35

1997-98

1.811

1.481

3.049

JULAUG,AUGSEP

2.3

OND, NDJ

31.01

2002-03

0.047

0.324

1.199

DECJAN

1.3

OND

16.49

2004-05

-0.020

0.747

1.055

FEBMAR

0.7

JAS-NDJ

37.25

2006-07

0.143

-0.322

1.322

OCTNOV

1.0

NDJ

3.21

2009-10

-0.103

0.303

1.521

JANFEB

1.3

NDJ,DJF

16.36

2014-156

-0.526

-0.297

0.997, 1.567

MAYJUN14, APRMAY15

0.6

OND, NDJ

8.52

2015-167

1.313

1.637

2.527

AUGSEP

2.3

NDJ

9.36

1. AAM and AAM tendency anomaly data for 1951-52 not available.
2. Continuous warm episode from DJF 1952/53 to DJF 1954.
3. AAM anomaly is average for Jan-Mar 1958.
4. Warm episode per ERSST.v4, but not ERSST.v3b.
5. Continuous warm episode from ASO 1986 to JFM 1988.
6. Warm episode per ERSST.v3b, but not ERSST.v4.
7. Data as of April 3, 2016.

Jul-Sep AAM & Nov-Mar AAM: The mean of the global relative atmospheric
angular momentum anomaly for the periods July 1 to September 30 amd November 1 to
March 31 of the following year. GWO phase space data is calculated using code from
the Global
Synoptic Dynamic Model page of the PSD Map Room Climate Products. Reference Weickmann
and Berry, 2008.

On the second go-round the upper low packed an even bigger
punch, producing strong afternoon thunderstorms with very high rain rates that resulted
in severe
flash flooding and debris flows in northern Los Angeles County and southern Kern
County.

Recall that storm a week ago Monday that blasted down
the West Coast and into the Southland? The Los Angeles County mountains received as
much as two inches of rain; Downtown Los Angeles (USC) recorded 0.45 inch of rain;
and the Sierra got a good shot of snow. (Here are some precipitation totals for that
storm from the NWS Los
Angeles/Oxnard and the NWS
San Diego.)

Downtown Los Angeles (USC) ended the 2014-2015 rainfall
year (July 1 - June 30) with 8.52 inches of rain; well below the normal of 14.93 inches.
It was the fourth consecutive year of below normal rainfall in Los Angeles and much
of Southern California.

Constructive interference of the El Nino base state by
the active phase of the MJO resulted in negative 200-hPa velocity potential anomalies
and enhanced convection in the Eastern Pacific during the first half of July. This
appears to have contributed to the rapid development of Dolores from a tropical depression
on July 11 into a Category 4 hurricane July 15. Anomalously warm SSTs in the tropical
and sub-tropical Eastern Pacific also played a role, helping to maintain the strength
of Dolores and increasing the amount of water vapor entrained by the system and transported
into Southern California.

Many stations set
new records, not only for the date, but for any day in July. Downtown Los Angeles
(USC) set rainfall records for the date on Saturday and Sunday and tied Monday's record.
Downtown Los Angeles recorded 0.36 inch of rain Saturday. This is more rain than any
day in any July since recordkeeping began in 1877. That one day of rainfall even broke
the monthly record for July in Los Angeles! Prior to this event the wettest July on
record was in 1886, when 0.24 inch was recorded.

Though the rain created its own problems -- including
flash floods, debris flows and rock slides -- the soaking rains helped quell the Pines
Fire near Wrightwood and the North Fire near Cajon Pass. Over the three day period
from Saturday to Monday the Big Pines Remote Automated Weather Station (RAWS), near
the Pines Fire, recorded 3.12 inches of rain. Several stations in the San Gabriels
recorded more than three inches of rain, including Clear Creek and Opids Camp. Here's
a NWS compilation of some rainfall totals in the Los
Angeles forecast area and the San
Diego forecast area.

After dawdling around for several months our on again,
off again El Nino is finally
firing on all cyclinders and could reach ONI and MEI levels not seen since 1997-98
and 1982-83. The Multivariate
ENSO Index (MEI) for May-June was 2.06. This was the third highest value for the
season, exceeded only in 1983 (2.2) and 1997 (2.3). It is the second highest for the
season during the development phase of an El Nino event. The 2015 April-May-June Oceanic
Nino Index (ONI) value of 0.9 was higher than than in 1982 (0.6) and 1997 (0.6).
Several dynamical models in the IRI/CPC
ENSO Predictions Plume of forecast Nino 3.4 SST anomaly, released July 16, project
Nino 3.4 SST anomalies in excess of 2.5°C this fall.

Analysis of correlations of CMAP Precipitation with globally
integrated atmospheric angular momentum using ESRL/PSD's Linear
Correlations in Atmospheric Seasonal/Monthly Averages tool suggests that precipitation
in the southern half of California is more strongly correlated with atmospheric angular
momentum (AAM) than with Nino 3.4 SST. For example, compare the correlation of CMAP
Precipitation to AAM and
to Nino
3.4 SST for Dec-Jan-Feb 1980-2012. Cyclical increases in relative atmospheric
angular momentum are often associated with El Ninos. This can be seen in the plots
of the Global Wind Oscillation in my El
Nino Comparison Chart.

After being negative for 3 1/2 years, the PDO
Index has been positive since January 2014. December's PDO value of 2.51 was the
highest for that month on record since 1900. June's value of 1.54 was the 13th highest
since 1900.

More information about Southern California weather and
climate can be found using our WEATHER LINKS page.

Southern California Weather Notes Copyright 2000-2017 Gary Valle. All Rights Reserved.
Fourth Year of Below Average Rainfall for Los Angeles. Southern California Begins Rain Year with Record-Setting July Storm. El Nino Finally Firing On All Cylinders. PDO Index Remains Positive.http://www.sierraphotography.com/wxnotes/PermaLink,guid,400e0eae-c039-4ce7-8318-db9b2671d82f.aspxhttp://www.sierraphotography.com/wxnotes/FourthYearOfBelowAverageRainfallForLosAngelesSouthernCaliforniaBeginsRainYearWithRecordSettingJulyStormElNinoFinallyFiringOnAllCylindersPDOIndexRemainsPositive.aspx
Tue, 28 Jul 2015 15:07:55 GMT
<div id="mainwx">
<div class="fltlft">
<p align="center">
<a title="NRL GOES E/W Composite VIS/IR (Day/Night) from Saturday, July 18, 2015 5:00 PM PDT with remnants of Hurricane Dolores off the coast of Baja. The remnants of Tropical Storm Enrique are farther to the west." href="wxdata1516/20150719.0000.goes_15.visir.bckgr_d.jpg" rel="wximage"> <img border="0" alt="NRL GOES E/W Composite VIS/IR (Day/Night) - Saturday, July 18, 2015 5:00 PM PDT" src="wxdata1516/20150719.0000.goes_15.visir.bckgr_c.jpg" width="300" height="220" /> </a> <img alt="Click" src="http://www.sierraphotography.com/wxnotes/images/click.gif" width="16" height="34" />
<br />
<span class="fontxxsmall">NRL GOES E/W Composite VIS/IR (Day/Night)<br />
Post-tropical remnant low Dolores is west of Baja<br />
Saturday, July 18, 2015 5:00 PM PDT. </span>
</p>
</div>
<p>
<span class="dropcap">D</span>owntown Los Angeles (USC) ended the 2014-2015 rainfall
year (July 1 - June 30) with 8.52 inches of rain; well below the normal of 14.93 inches.
It was the fourth consecutive year of below normal rainfall in Los Angeles and much
of Southern California.
</p>
<p>
<span class="dropcap">T</span>o kick off the new new rainfall year two waves of moisture
and instability associated with <a href="wxdata1516/20150719.0000.goes15.vapor.x.pacus.x.jpg" rel="wximage" target="_blank">ex-hurricane
Dolores, other tropical sources, and a strong monsoonal flow from Baja</a> resulted
in record-setting rainfall in Southern California from Saturday July 18 to Monday
July 20.
</p>
<p>
<span class="dropcap">C</span>onstructive interference of the El Nino base state by
the active phase of the MJO resulted in negative 200-hPa velocity potential anomalies
and enhanced convection in the Eastern Pacific during the first half of July. This
appears to have contributed to the rapid development of Dolores from a tropical depression
on July 11 into a Category 4 hurricane July 15. Anomalously warm SSTs in the tropical
and sub-tropical Eastern Pacific also played a role, helping to maintain the strength
of Dolores and increasing the amount of water vapor entrained by the system and transported
into Southern California.
</p>
<p>
<span class="dropcap">M</span>any stations <a href="wxdata1516/RERLOX072015_0541PDT.pdf" target="_blank">set
new records</a>, not only for the date, but for any day in July. Downtown Los Angeles
(USC) set rainfall records for the date on Saturday and Sunday and tied Monday's record.
Downtown Los Angeles recorded 0.36 inch of rain Saturday. This is more rain than any
day in any July since recordkeeping began in 1877. That one day of rainfall even broke
the monthly record for July in Los Angeles! Prior to this event the wettest July on
record was in 1886, when 0.24 inch was recorded.
</p>
<p>
<span class="dropcap">T</span>here was <a href="wxdata1516/UCAR_NEXRAD_KSOX_072015_0100zb.png" rel="wximage" target="_blank">very
heavy rain in the mountains on Sunday</a>, with rain rates exceeding an inch a hour.
From 5:15 p.m. to 5:25 p.m. a <a href="http://www.wunderground.com/personal-weather-station/dashboard?ID=KCAMOUNT12#history" target="_blank">CBS
Radio weather station on Mt. Wilson</a> recorded a half-inch of rain in just 10 minutes!
</p>
<p>
<span class="dropcap">T</span>hough the rain created its own problems -- including
flash floods, debris flows and rock slides -- the soaking rains helped quell the Pines
Fire near Wrightwood and the North Fire near Cajon Pass. Over the three day period
from Saturday to Monday the Big Pines Remote Automated Weather Station (RAWS), near
the Pines Fire, recorded 3.12 inches of rain. Several stations in the San Gabriels
recorded more than three inches of rain, including Clear Creek and Opids Camp. Here's
a NWS compilation of some rainfall totals in the <a href="wxdata1516/RRMLOX072015_1757PDT.pdf" target="_blank">Los
Angeles forecast area</a> and the <a href="wxdata1516/RRMSGX071915_1930PDT.pdf" target="_blank">San
Diego forecast area</a>.
</p>
<p>
<span class="dropcap">A</span>fter dawdling around for several months our on again,
off again El Nino is <a href="wxdata1516/sst_wind_anom_5day_ps32_072715b.gif" rel="wximage" target="_blank">finally
firing on all cyclinders</a> and could reach ONI and MEI levels not seen since 1997-98
and 1982-83. The <a href="http://www.esrl.noaa.gov/psd/enso/mei/index.html" target="_blank">Multivariate
ENSO Index</a> (MEI) for May-June was 2.06. This was the third highest value for the
season, exceeded only in 1983 (2.2) and 1997 (2.3). It is the second highest for the
season during the development phase of an El Nino event. The 2015 April-May-June <a href="http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/ensostuff/ensoyears.shtml" target="_blank">Oceanic
Nino Index</a> (ONI) value of 0.9 was higher than than in 1982 (0.6) and 1997 (0.6).
Several dynamical models in the <a href="wxdata1516/IRI-CPC_ENSOPlume071615b.gif" rel="wximage" target="_blank">IRI/CPC
ENSO Predictions Plume of forecast Nino 3.4 SST anomaly</a>, released July 16, project
Nino 3.4 SST anomalies in excess of 2.5°C this fall.
</p>
<p>
<span class="dropcap">A</span>nalysis of correlations of CMAP Precipitation with globally
integrated atmospheric angular momentum using ESRL/PSD's <a href="http://www.esrl.noaa.gov/psd/data/correlation/" target="_blank">Linear
Correlations in Atmospheric Seasonal/Monthly Averages tool</a> suggests that precipitation
in the southern half of California is more strongly correlated with atmospheric angular
momentum (AAM) than with Nino 3.4 SST. For example, compare the correlation of CMAP
Precipitation to <a href="wxdata1516/CorrDecFeb1980_2012_Precip_AAMb.gif" rel="wximage" target="_blank">AAM</a> and
to <a href="wxdata1516/CorrDecFeb1980_2012_Precip_Nino34b.gif" rel="wximage" target="_blank">Nino
3.4 SST</a> for Dec-Jan-Feb 1980-2012. Cyclical increases in relative atmospheric
angular momentum are often associated with El Ninos. This can be seen in the plots
of the Global Wind Oscillation in my <a href="http://www.sierraphotography.com/wxnotes/ElNinoComparisonChartFor20142015.aspx" target="_blank">El
Nino Comparison Chart</a>.
</p>
<p>
<span class="dropcap">A</span>fter being negative for 3 1/2 years, the <a href="http://jisao.washington.edu/pdo/" target="_blank">PDO
Index</a> has been positive since January 2014. December's PDO value of 2.51 was the
highest for that month on record since 1900. June's value of 1.54 was the 13th highest
since 1900.
</p>
<p>
<span class="dropcap">M</span>ore information about Southern California weather and
climate can be found using our <a href="weatherlinks.htm">WEATHER LINKS</a> page.
</p>
<p>
</p>
</div>
<img width="0" height="0" src="http://www.sierraphotography.com/wxnotes/aggbug.ashx?id=400e0eae-c039-4ce7-8318-db9b2671d82f" />
<br />
<hr />Southern California Weather Notes Copyright 2000-2017 Gary Valle. All Rights Reserved.climateEl Ninoflash floodGlobal Wind Oscillation (GWO)Los Angeles rainfallMadden-Julian Oscillation (MJO)Multivariate ENSO Index (MEI)record rainfallweatherhttp://www.sierraphotography.com/wxnotes/Trackback.aspx?guid=7d519dab-e8b2-4314-92d7-56c7789bd70bhttp://www.sierraphotography.com/wxnotes/pingback.aspxhttp://www.sierraphotography.com/wxnotes/PermaLink,guid,7d519dab-e8b2-4314-92d7-56c7789bd70b.aspxGary Valle

Following is a chart comparing 2014-15 to warm ENSO episodes
that have occurred since 1950. The warm episodes are based on the revised Oceanic
Niño Index (ONI) which is calculated using the three month running mean of ERSST.v4
SST anomalies in the Niño 3.4 region with multiple-centered 30 year base periods.
Unless noted the warm episodes are those specified in the CPC's tabulation of Cold
& Warm Episodes by Season. A description of the parameters follows the chart.
With the exception of years prior to 1957, a GWO phase space plot is included for
each warm episode.

Jul-Sep AAM & Nov-Mar AAM: The mean of the global relative atmospheric
angular momentum anomaly for the periods July 1 to September 30 amd November 1 to
March 31 of the following year. Data is from the GWO phase space data file linked
on the Global
Synoptic Dynamic Model page of the PSD Map Room Climate Products. Reference Weickmann
and Berry, 2008.

Current Departure from Normal Precipitation Since October
1
AHPS Precpitation Analysis as of 1/19/2015 12:00 UTC.

After being negative for 3 1/2 years, the PDO
Index has been positive since January 2014. December's PDO value of 2.51 is the
highest for that month on record (since 1900), exceeding December 2002's value of
2.10 and December 1940's value of 1.96.

Even so, the highly anticipated 2014-15 El Nino continues
to dawdle with little ocean-atmosphere coupling and an emphasis on an higher amplitude
meridional flows. Due in part to the upwelling phase of a series of oceanic Kelvin
waves, equatorial Pacific heat content and SST anomalies have diminished. After having
been at or above 0.5 °C for the past twelve weeks OISST.v2
Nino 3.4 SST Anomalies dropped to 0.4 °C for the week centered on January 7, 2015
and as of the week of January 14 was at 0.5 °C.

So far this rain season Northern California and the coastal
areas of Central and Southern California have fared much better in terms of precipitation
than last year. As of today Downtown Los Angeles (USC) precipitation for the water
year (beginning July 1) is at 90% of normal and Downtown San Francisco is at 127%.

At the moment it doesn't look like the snowpack will
get much help in the short term. After fending off a little shortwave the blocking
ridge is forecast to rebuild to new heights, bringing unseasonably mild weather to
much of the West Coast. There does appear to be the possibility of a wildcard low
latitude low developing under the block and that could result in some precipitation
in Southern California next week. If such a system develops, given the warm state
of the Eastern Pacific, it could be wetter than expected. We'll see!

In the early morning hours of Friday, December 12, 2014,
a very strong cold front, enhanced with moisture from an atmospheric river, produced
a line of strong storms that produced rain rates in the Springs Fire burn area as
high as 2 inches per hour. This resulted in widespread flash floods and debris flows
in the burn area, much of which is in Pt. Mugu State Park. Mud and debris flows originating
from the burn area inundated homes below Conejo Mountain and closed Pacific Coast
Highway. This slideshow
includes photos of the aftermath of the flash floods and debris flows in Blue
Canyon, Sycamore Canyon and Upper Sycamore. The photos were taken on a trail run on
December 14, 2014. Also included are some NWS Los Angeles/Oxnard tweets and some additional
meteorological images and info.

More information about Southern California weather and
climate can be found using our WEATHER LINKS page.

Southern California Weather Notes Copyright 2000-2017 Gary Valle. All Rights Reserved.
PDO Index the Highest on Record for December. El Nino Continues to Dawdle. Coastal California vs Sierra Precipitation. Pt. Mugu State Park Flash Floods & Debris Flows.http://www.sierraphotography.com/wxnotes/PermaLink,guid,7728b83e-4978-41c4-98d7-4ffd907553ca.aspxhttp://www.sierraphotography.com/wxnotes/PDOIndexTheHighestOnRecordForDecemberElNinoContinuesToDawdleCoastalCaliforniaVsSierraPrecipitationPtMuguStateParkFlashFloodsDebrisFlows.aspx
Tue, 20 Jan 2015 16:44:31 GMT
<div id="mainwx">
<div class="fltlft">
<p align="center">
<a title="Southwestern U.S. Current Departure from Normal Precipitation Since October 1 as of 1/19/2015 12:00 UTC." href="wxdata1415/WY_Oct1_Precip_Depart_011915_12zb.png" rel="wximage"> <img border="0" alt="Southwestern U.S. Current Departure from Normal Precipitation Since October 1 as of 1/19/2015 12:00 UTC." src="wxdata1415/WY_Oct1_Precip_Depart_011915_12zc.png" width="350" height="215" /> </a> <img alt="Click" src="http://www.sierraphotography.com/wxnotes/images/click.gif" width="16" height="34" />
<br />
<span class="fontxxsmall">Current Departure from Normal Precipitation Since October
1<br />
AHPS Precpitation Analysis as of 1/19/2015 12:00 UTC. </span>
</p>
</div>
<p>
<span class="dropcap">A</span>fter being negative for 3 1/2 years, the <a href="http://jisao.washington.edu/pdo/" target="_blank">PDO
Index</a> has been positive since January 2014. December's PDO value of 2.51 is the
highest for that month on record (since 1900), exceeding December 2002's value of
2.10 and December 1940's value of 1.96.
</p>
<p>
<span class="dropcap">E</span>ven so, the highly anticipated 2014-15 El Nino continues
to dawdle with little ocean-atmosphere coupling and an emphasis on an higher amplitude
meridional flows. Due in part to the upwelling phase of a series of oceanic Kelvin
waves, equatorial Pacific heat content and SST anomalies have diminished. After having
been at or above 0.5 °C for the past twelve weeks <a href="http://www.cpc.ncep.noaa.gov/data/indices/wksst8110.for" target="_blank">OISST.v2
Nino 3.4 SST Anomalies</a> dropped to 0.4 °C for the week centered on January 7, 2015
and as of the week of January 14 was at 0.5 °C.
</p>
<p>
<span class="dropcap">T</span>he <a href="http://www.esrl.noaa.gov/psd/enso/mei/index.html" target="_blank">Multivariate
ENSO Index</a> (MEI) for NOV/DEC has decreased 0.13 SD to +0.58, but has maintained
its historic rank (since 1950) at 47. A rank of 46 is the threshold for weak El Nino
conditions in the context of the MEI. The <a href="wxdata1415/psd_gwo_fnl_011915b.png" rel="wximage" target="_blank">FNL
Global Wind Oscillation for the past 90 days</a> continues to reflect the lack of
definitive atmospheric coupling.
</p>
<p>
<span class="dropcap">S</span>o far this rain season Northern California and the coastal
areas of Central and Southern California have fared much better in terms of precipitation
than last year. As of today Downtown Los Angeles (USC) precipitation for the water
year (beginning July 1) is at 90% of normal and Downtown San Francisco is at 127%.
</p>
<p>
<span class="dropcap">A</span>s this AHPS plot of <a href="wxdata1415/WY_Oct1_Precip_PON_011915_12zb.png" rel="wximage" target="_blank">precipitation
since October 1</a> shows, many areas of California have recorded at least 75% of
normal precipitation. Unfortunately the Sierra Nevada is not one of them. While better
than <a href="http://cdec.water.ca.gov/cgi-progs/reports/DLYSWEQ.20140120" target="_blank">last
year's dismal 14% of normal on this date</a>, this year's snowpack is currently well
below average, and was<a href="http://cdec.water.ca.gov/cgi-progs/reports/DLYSWEQ.20150115" target="_blank"> last
reported at 36%</a>. Here is an AHPS plot of <a href="wxdata1415/WY_Oct1_Precip_Depart_011915_12zb.png" rel="wximage" target="_blank">precipitation
departure since October 1</a> that shows the deficits in the Sierra Nevada.
</p>
<p>
<span class="dropcap">A</span>t the moment it doesn't look like the snowpack will
get much help in the short term. After fending off a little shortwave the blocking
ridge is forecast to rebuild to new heights, bringing unseasonably mild weather to
much of the West Coast. There does appear to be the possibility of a wildcard low
latitude low developing under the block and that could result in some precipitation
in Southern California next week. If such a system develops, given the warm state
of the Eastern Pacific, it could be wetter than expected. We'll see!
</p>
<p>
<span class="dropcap">I</span>n the early morning hours of Friday, December 12, 2014,
a very strong cold front, enhanced with moisture from an atmospheric river, produced
a line of strong storms that produced rain rates in the Springs Fire burn area as
high as 2 inches per hour. This resulted in widespread flash floods and debris flows
in the burn area, much of which is in Pt. Mugu State Park. Mud and debris flows originating
from the burn area inundated homes below Conejo Mountain and closed Pacific Coast
Highway. This <a href="http://www.photographyontherun.com/ssprun.asp?id=1305" target="_blank">slideshow
includes photos of the aftermath of the flash floods and debris flows</a> in Blue
Canyon, Sycamore Canyon and Upper Sycamore. The photos were taken on a trail run on
December 14, 2014. Also included are some NWS Los Angeles/Oxnard tweets and some additional
meteorological images and info.
</p>
<p>
<span class="dropcap">M</span>ore information about Southern California weather and
climate can be found using our <a href="weatherlinks.htm">WEATHER LINKS</a> page.
</p>
<p>
</p>
</div>
<img width="0" height="0" src="http://www.sierraphotography.com/wxnotes/aggbug.ashx?id=7728b83e-4978-41c4-98d7-4ffd907553ca" />
<br />
<hr />Southern California Weather Notes Copyright 2000-2017 Gary Valle. All Rights Reserved.climateEl NinoGlobal Wind Oscillation (GWO)Los Angeles rainfallMultivariate ENSO Index (MEI)precipitation outlookSierra snowpackweatherhttp://www.sierraphotography.com/wxnotes/Trackback.aspx?guid=d6efcb6a-0ca4-4210-bccf-e045770be27chttp://www.sierraphotography.com/wxnotes/pingback.aspxhttp://www.sierraphotography.com/wxnotes/PermaLink,guid,d6efcb6a-0ca4-4210-bccf-e045770be27c.aspxGary Valle

After being negative for 3 1/2 years, the PDO
Index has been positive since January 2014. October's PDO value of 1.49 is the
6th highest for that month since 1900 and comparable to PDO Index values in October
1997, 1957, 1993, and 1987.

A warm Pacific may have contributed to the amount of
precipitation produced in California by a large
Pacific upper level low this past week. Two periods of rain were observed in Southern
California -- one on Sunday and the other on Tuesday and Wednesday.

Even with the parent low lifting
to the north on Tuesday and the 570 mb contour near Santa Barbara, the very
moist southerly flow orographic lift and sufficient dynamics produced widespread
precipitation in Southern California with some impressive precipitation totals. Tuesday
record rainfall for the date occurred at both Downtown Los Angeles and Downtown San
Francisco. Yucaipa Ridge in the San Bernardino Mountains recorded a whopping three-day
rainfall total of 14.6 inches. Following are three-day rainfall compilations from
the NWS Los Angeles/Oxnard and NWS
San Diego.

Here are graphics from the CNRFC with gridded precipitation
totals for the four day period from early Sunday morning to early Thursday morning
for Southern
California, the Sierra
Nevada and the San
Francisco Bay Area. Some preliminary precipitation totals of 5 inches or more
are noted.

One thing is very clear; we have a lot to learn about
the atmosphere's response to anomalously warm equatorial Pacific SSTs. It's difficult
to imagine a better scenario for El Niño development than the conditions seen in the
equatorial Pacific earlier this year.

The Oceanic
Niño Index (ONI) jumped from -0.5 in the FMA season to -0.1 in MAM, and then to
+0.1 in AMJ. During that same period the Multivariate
ENSO Index (MEI) jumped from a rank of 35 in MARAPR to 59 in APRMAY -- a value
that put it on the doorstep of a strong El Nino ranking. Which all looked supportive
of at least a moderate El Nino developing.

But it didn't. After climbing up to 0.6 °C in late May, Nino
3.4 region SST anomalies dropped to below 0.0 °C in late July. Since then a more
modest downwelling Kelvin wave has restored some of the basin heat content and Nino
3.4 anomalies have rebounded back to 0.6 °C.

So what's next? While El Nino development still appears
to be possible this Winter, it would be one of the two latest developing El Ninos
in the record from 1950 to the present -- the other being 1952-53. One possibility
is that this year's vacillations are the precursor to the EARLY development of an
El Nino event next year.

The 1981-2010 climate normal average rainfall for Downtown
Los Angeles in November is 1.04 inches. Month to date we're about average for the
date, and water year to date we're ahead of last year, but about 0.6 inch below normal.

Based on the current GFS and ECMWF forecasts those deficits
are probably going to increase over the next two weeks, but it is way too early in
the rain season to attribute the dry weather to a continued dry pattern. El Niño or
not; dry November or not; the switch from a cold Pacific to a warm Pacific is a significant
change and one that some guidance suggests should increase our rainfall. We'll see!

More information about Southern California weather and
climate can be found using our WEATHER LINKS page.

Southern California Weather Notes Copyright 2000-2017 Gary Valle. All Rights Reserved.
Another El Nino Near Miss? Fast-Moving Front and Trough Brings a Shot of Rain & Snow to California. Dry Rain Season Ahead for Southern California?http://www.sierraphotography.com/wxnotes/PermaLink,guid,1d92dc62-2cc3-493a-82d3-a91e6977756d.aspxhttp://www.sierraphotography.com/wxnotes/AnotherElNinoNearMissFastMovingFrontAndTroughBringsAShotOfRainSnowToCaliforniaDryRainSeasonAheadForSouthernCalifornia.aspx
Fri, 07 Nov 2014 22:18:36 GMT
<div id="mainwx">
<div class="fltlft">
<p align="center">
<a title="SST NINO Region Anomalies from the CPC ENSO Diagnostic Discussion 11/6/2014." href="wxdata1415/cpc_ninoregionanom103014b.gif" rel="wximage"> <img border="0" alt="SST NINO Region Anomalies from the CPC ENSO Diagnostic Discussion 11/6/2014." src="wxdata1415/cpc_ninoregionanom103014c.jpg" width="300" height="374" /> </a> <img alt="Click" src="http://www.sierraphotography.com/wxnotes/images/click.gif" width="16" height="34" />
<br />
<span class="fontxxsmall">SST NINO Region Anomalies<br />
From the CPC ENSO Diagnostic Discussion 11/6/2014. </span>
</p>
</div>
<p>
<span class="dropcap">O</span>ne thing is very clear; we have a lot to learn about
the atmosphere's response to anomalously warm equatorial Pacific SSTs. It's difficult
to imagine a better scenario for El Niño development than the conditions seen in the
equatorial Pacific earlier this year.
</p>
<p>
<span class="dropcap">A</span>fter being negative for 42 out of the previous 43 months,
the <a href="http://jisao.washington.edu/pdo/" target="_blank">Pacific Decadal Oscillation</a> (PDO)
index turned positive in January 2014 and has remained positive through the summer.
Beginning in January and ending in late June the downwelling phase of a <a href="wxdata1415/cpc_tlon_heatanom103014b.gif" rel="wximage" target="_blank">very
strong Kelvin wave</a> propagated across the Pacific, with <a title="From the CPC ENSO Diagnostic Discussion 11/6/2014." href="wxdata1415/cpc_heat-last-year103014b.gif" rel="wximage" target="_blank">upper
ocean area-averaged heat content anomaly</a> between 180 and 100W peaking at the end
of March. Since January there have been westerly wind bursts and <a href="wxdata1415/time_lon_EQ_hf_uwnd_uwnd_mean_anom_201211_201411_2014110709b.gif" rel="wximage" target="_blank">periods
of increased low-level westerly zonal wind anomalies</a> of variable duration and
extent.
</p>
<p>
<span class="dropcap">T</span>he <a href="http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/ensostuff/ensoyears.shtml" target="_blank">Oceanic
Niño Index (ONI)</a> jumped from -0.5 in the FMA season to -0.1 in MAM, and then to
+0.1 in AMJ. During that same period the <a href="http://www.esrl.noaa.gov/psd/enso/mei/index.html" target="_blank">Multivariate
ENSO Index</a> (MEI) jumped from a rank of 35 in MARAPR to 59 in APRMAY -- a value
that put it on the doorstep of a strong El Nino ranking. Which all looked supportive
of at least a moderate El Nino developing.
</p>
<p>
<span class="dropcap">B</span>ut it didn't. After climbing up to 0.6 °C in late May, <a title="SST NINO Region Anomalies from the CPC ENSO Diagnostic Discussion 11/6/2014." href="wxdata1415/cpc_ninoregionanom103014b.gif" rel="wximage" target="_blank">Nino
3.4 region SST anomalies</a> dropped to below 0.0 °C in late July. Since then a more
modest downwelling Kelvin wave has restored some of the basin heat content and Nino
3.4 anomalies have rebounded back to 0.6 °C.
</p>
<p>
<span class="dropcap">S</span>o what's next? While El Nino development still appears
to be possible this Winter, it would be one of the two latest developing El Ninos
in the record from 1950 to the present -- the other being 1952-53. One possibility
is that this year's vacillations are the precursor to the EARLY development of an
El Nino event next year.
</p>
<p>
<span class="dropcap">O</span>ne worrisome detail is that the <a href="http://www.esrl.noaa.gov/psd/map/clim/test_maproom.html" target="_blank">Global
Wind Oscillation</a> (GWO) has been behaving similarly to the failed El Nino of 2012.
Compare this plot of the <a href="wxdata1415/gwo_060114_103114b.png" rel="wximage" target="_blank">GWO
from June 1 to October 31 of this year</a> to the plot of the <a href="wxdata1415/gwo_060112_103112b.png" rel="wximage" target="_blank">GWO
from June 1 to October 31, 2012</a>. In both 2014 and 2012 the GWO has shown a neutral
or weak La Nina-like response. The <a href="wxdata1415/gwo_060197_103197b.png" rel="wximage" target="_blank">GWO
for the period June 1 to October 31, 1997</a> is an example of a definitive atmospheric
response to strong El Nino conditions.
</p>
<p>
<span class="dropcap">O</span>n a more positive note, a <a href="wxdata1415/UCAR_NEXRAD_110114_0700zb.png" rel="wximage" target="_blank">relatively
strong</a>, but fast-moving <a href="wxdata1415/ramdis_gwir404_20141101070000b.gif" rel="wximage" target="_blank">Pacific
cold front and trough</a> resulted in <a href="wxdata1415/CNRFC_7Day_QPE_110714_12zb.jpg" rel="wximage" target="_blank">rain
and snow in California</a> over Halloween. In the Los Angeles area rainfall amounts
generally <a href="wxdata1415/CNRFC_Precip_raw_110114b.jpg" rel="wximage" target="_blank">varied
from around 0.3 inch to 0.75 inch</a> or so with isolated amounts as high as about
2.0 inches in the mountains. Here are some tabulated rainfall amounts from around
the area from the <a href="wxdata1415/RRMLOX110114_1905PST.pdf" target="_blank">NWS
Los Angeles/Oxnard</a> and <a href="wxdata1415/RRMSGX110214_1030PDT.pdf" target="_blank">NWS
San Diego</a>.
</p>
<p>
<span class="dropcap">T</span>he 1981-2010 climate normal average rainfall for Downtown
Los Angeles in November is 1.04 inches. Month to date we're about average for the
date, and water year to date we're ahead of last year, but about 0.6 inch below normal.
</p>
<p>
<span class="dropcap">B</span>ased on the current GFS and ECMWF forecasts those deficits
are probably going to increase over the next two weeks, but it is way too early in
the rain season to attribute the dry weather to a continued dry pattern. El Niño or
not; dry November or not; the switch from a cold Pacific to a warm Pacific is a significant
change and one that some guidance suggests should increase our rainfall. We'll see!
</p>
<p>
<span class="dropcap">M</span>ore information about Southern California weather and
climate can be found using our <a href="weatherlinks.htm">WEATHER LINKS</a> page.
</p>
<p>
</p>
</div>
<img width="0" height="0" src="http://www.sierraphotography.com/wxnotes/aggbug.ashx?id=1d92dc62-2cc3-493a-82d3-a91e6977756d" />
<br />
<hr />Southern California Weather Notes Copyright 2000-2017 Gary Valle. All Rights Reserved.climateEl NinoGlobal Wind Oscillation (GWO)Los Angeles rainfallMultivariate ENSO Index (MEI)precipitation outlookweatherWesterly Wind Burst (WWB)http://www.sierraphotography.com/wxnotes/Trackback.aspx?guid=cda8bd7e-f74e-4206-b3c3-380791d0b5fchttp://www.sierraphotography.com/wxnotes/pingback.aspxhttp://www.sierraphotography.com/wxnotes/PermaLink,guid,cda8bd7e-f74e-4206-b3c3-380791d0b5fc.aspxGary Valle

The "PDO minus AMO" composite precipitation anomaly maps
prepared by Dr. Klaus Wolter of CIRES as part of an experimental
seasonal forecast for the California DWR last year were consistent with the below
average precipitation observed in California in the water years Oct 2012 - Sep 2013
and Oct 2013 - Sep 2014.

As referenced in Dr.
Wolter's 2013 DWR presentation, Schubert et al. (J. Climate, 2009) found that
five global climate models produced the least precipitation in the continental U.S.
when the Pacific is cold (Pc) and the Atlantic warm (Aw). Conversely four of the five
models produced the wettest conditions when the Pacific is warm (Pw) and Atlantic
cold (Ac). As shown
in this figure, all combinations with the Pacific cold (PcAw, PcAn, PcAc) produced
below average precipitation and all combinations with the Pacific warm (PwAw, PwAn,
PwAc) produced above average precipitation.

While the development of the 2014 El Nino has waxed and
waned over the past several months, there has been a definitive change that might
significantly impact the weather in California and the U.S. -- the Pacific has warmed.
For five of the past six years the JUL-SEP PDO has been negative. This year the PDO
has been positive since January.

To get an idea of how the change to a warm Pacific might
affect precipitation in the U.S. the PDO index and AMO index values for JUL-SEP for
the past 115 years were ranked and then divided into tercile classes, producing nine
PDO/AMO states.

The PwAw composites show much more precipitation in Southern
California and the Southwestern U.S. than the PcAw composites. It might be argued
that it is the El Nino years in the PwAw composites that produce the wet signal in
Southern California. However, if the El Nino years are removed from the PwAw composites
for Oct-Sep and composites
for Dec-Feb, a wet signal persists.

Of course there are many factors that can influence the
amount of precipitation in a particular locale in a particular season or water year.
Composites are not forecasts any more than monthly climate normals are forecasts;
but both can provide useful guidance. In the PwAw case 7 of the 12 selected years
in the composite were wet in Southern California and two-thirds of the years had near
normal or above average precipitation. We'll see what happens in 2014-2015.

More information about Southern California weather and
climate can be found using our WEATHER LINKS page.

Southern California Weather Notes Copyright 2000-2017 Gary Valle. All Rights Reserved.
U.S. Composite Precipitation Anomalies Based on PDO and AMO Support Possibility of Wet Rain Season in Southern California.http://www.sierraphotography.com/wxnotes/PermaLink,guid,cda8bd7e-f74e-4206-b3c3-380791d0b5fc.aspxhttp://www.sierraphotography.com/wxnotes/USCompositePrecipitationAnomaliesBasedOnPDOAndAMOSupportPossibilityOfWetRainSeasonInSouthernCalifornia.aspx
Sat, 01 Nov 2014 20:58:59 GMT
<div id="mainwx">
<div class="fltlft">
<p align="center">
<a title="Warm Pacific/Warm Atlantic Composite Precipitation Anomaly based on JUL-SEP PDO Index and AMO Index." href="wxdata1415/PDO_AMO_OctSep_PwAwb.png" rel="wximage"> <img border="0" alt="Warm Pacific/Warm Atlantic Composite Precipitation Anomaly" src="wxdata1415/PDO_AMO_OctSep_PwAwc.png" width="300" height="258" /> </a> <img alt="Click" src="http://www.sierraphotography.com/wxnotes/images/click.gif" width="16" height="34" />
<br />
<span class="fontxxsmall">Warm Pacific/Warm Atlantic Composite Precipitation Anomaly<br />
Based on JUL-SEP PDO Index and AMO Index. </span>
</p>
</div>
<p>
<span class="dropcap">T</span>he "PDO minus AMO" composite precipitation anomaly maps
prepared by Dr. Klaus Wolter of CIRES as part of an <a href="http://www.water.ca.gov/news/newsreleases/2013/112513.pdf" target="_blank">experimental
seasonal forecast</a> for the California DWR last year were consistent with the below
average precipitation observed in California in the water years Oct 2012 - Sep 2013
and Oct 2013 - Sep 2014.
</p>
<p>
<span class="dropcap">A</span>s referenced in <a href="http://www.water.ca.gov/waterconditions/drought/docs/Winter%20Outlook%202013.pdf" target="_blank">Dr.
Wolter's 2013 DWR presentation</a>, Schubert et al. (J. Climate, 2009) found that
five global climate models produced the least precipitation in the continental U.S.
when the Pacific is cold (Pc) and the Atlantic warm (Aw). Conversely four of the five
models produced the wettest conditions when the Pacific is warm (Pw) and Atlantic
cold (Ac). As <a href="wxdata1415/Schubert2009GCMPrecip.png" rel="wximage" target="_blank">shown
in this figure</a>, all combinations with the Pacific cold (PcAw, PcAn, PcAc) produced
below average precipitation and all combinations with the Pacific warm (PwAw, PwAn,
PwAc) produced above average precipitation.
</p>
<p>
<span class="dropcap">W</span>hile the development of the 2014 El Nino has waxed and
waned over the past several months, there has been a definitive change that might
significantly impact the weather in California and the U.S. -- the Pacific has warmed.
For five of the past six years the JUL-SEP PDO has been negative. This year the PDO
has been positive since January.
</p>
<p>
<span class="dropcap">T</span>o get an idea of how the change to a warm Pacific might
affect precipitation in the U.S. the PDO index and AMO index values for JUL-SEP for
the past 115 years were ranked and then divided into tercile classes, producing nine
PDO/AMO states.
</p>
<p>
<span class="dropcap">T</span>he <a href="http://www.esrl.noaa.gov/psd/data/usclimdivs/" target="_blank">NOAA/NCDC
Climate Division Mapping and Analysis Web Tool</a> was then used to generate composite
precipitation maps for <a href="wxdata1415/PDO_AMO_OctSep_Comp.png" rel="wximage" target="_blank">October
to September</a> and<a href="wxdata1415/PDO_AMO_DecFeb_Comp.png" rel="wximage" target="_blank"> December
to January</a> for the six combinations of Pacific warm and Pacific cold states: PwAw,
PwAn, PwAc and PcAw, PcAn, PcAc.
</p>
<p>
<span class="dropcap">T</span>he PwAw composites show much more precipitation in Southern
California and the Southwestern U.S. than the PcAw composites. It might be argued
that it is the El Nino years in the PwAw composites that produce the wet signal in
Southern California. However, if the El Nino years are removed from the PwAw <a href="wxdata1415/PDO_AMO_OctSep_NoElNinoYrs.png" rel="wximage" target="_blank">composites
for Oct-Sep</a> and <a href="wxdata1415/PDO_AMO_DecFeb_NoElNinoYrs.png" rel="wximage" target="_blank">composites
for Dec-Feb</a>, a wet signal persists.
</p>
<p>
<span class="dropcap">O</span>f course there are many factors that can influence the
amount of precipitation in a particular locale in a particular season or water year.
Composites are not forecasts any more than monthly climate normals are forecasts;
but both can provide useful guidance. In the PwAw case 7 of the 12 selected years
in the composite were wet in Southern California and two-thirds of the years had near
normal or above average precipitation. We'll see what happens in 2014-2015.
</p>
<p>
<span class="dropcap">M</span>ore information about Southern California weather and
climate can be found using our <a href="weatherlinks.htm">WEATHER LINKS</a> page.
</p>
<p>
</p>
</div>
<img width="0" height="0" src="http://www.sierraphotography.com/wxnotes/aggbug.ashx?id=cda8bd7e-f74e-4206-b3c3-380791d0b5fc" />
<br />
<hr />Southern California Weather Notes Copyright 2000-2017 Gary Valle. All Rights Reserved.climateEl NinoLos Angeles rainfallprecipitation outlookweatherhttp://www.sierraphotography.com/wxnotes/Trackback.aspx?guid=d3d30989-63e9-4c81-95ae-9bba8f08fbddhttp://www.sierraphotography.com/wxnotes/pingback.aspxhttp://www.sierraphotography.com/wxnotes/PermaLink,guid,d3d30989-63e9-4c81-95ae-9bba8f08fbdd.aspxGary Valle

Two-Year Percentage of Normal Precipitation
July 1, 2012 to June 30, 2014 (WRCC).

Downtown Los Angeles (USC) finished the water year (July
1 to June 30) with 6.08 inches of recorded rainfall. This is about 41% of the 1981-2010
normal of 14.93 inches. It was the seventh driest water year since recordkeeping began
in 1877. When combined with last year's water year total of 5.85 inches, the back-to-back
water years from July 1, 2012 to June 30, 2014 are the driest on record for Los Angeles.
The total rainfall deficit over the two year period was about 18 inches.

El Nino has been knocking on the door, but until very
recently the atmosphere has only been responding in spits and sputters.

The weekly OISST.v2
Nino 3.4 SST temperature anomaly has been vacillating in the range 0.4 to 0.6
beginning with the week centered on April 23, 2014 and now stands at 0.5. Nino 1+2
and Nino 3 anomalies have generally been increasing and as of the week centered on
June 25 are at 1.6 and 1.0 respectively. Here is a plot
of the Nino regions SST anomalies from the CPC. Following a period of strengthened
tradewinds, another westerly wind burst has developed in the Western Pacific. There
have been several
WWB this year and the most recent WWB could lead to additional warming of equatorial
SSTs.

The Global
Wind Oscillation (GWO) can be a useful tool for evaluating the degree to which
the atmosphere is responding to El Nino or La Nina conditions. As this plot of the GWO
for the period March 1 to July 31, 1997 shows, during the spring and summer of
1997 El Nino conditions were already resulting in a definitive atmospheric response.
Here is a plot of the GWO
from March 1 to July 1 of this year. Over most of this period the GWO has shown
a neutral or weak La Nina-like response. Recently the GWO has exhibited a positive
shift in AAM anomaly that, if sustained, could be indicative of a coupled ocean-atmosphere
response.

The Plume-based and Consensus Forecasts in the June
19 IRI/CPC ENSO Quick Look (PDF) show an increasing chance of El Nino conditions
developing over the NH summer, with an approximately 80% chance of El Nino conditions
being established by the OND season. A July
2 run of the CFSv2 forecasts Nino 3.4 anomalies to briefly decline, then increase
substantially from July into October. We'll see!

More information about Southern California weather and
climate can be found using our WEATHER LINKS page.

Southern California Weather Notes Copyright 2000-2017 Gary Valle. All Rights Reserved.
Los Angeles Experiences Driest Back-to-Back Water Years On Record. Transition to Fully-Developed El Nino In Progress.http://www.sierraphotography.com/wxnotes/PermaLink,guid,d3d30989-63e9-4c81-95ae-9bba8f08fbdd.aspxhttp://www.sierraphotography.com/wxnotes/LosAngelesExperiencesDriestBacktoBackWaterYearsOnRecordTransitionToFullyDevelopedElNinoInProgress.aspx
Thu, 03 Jul 2014 20:48:36 GMT
<div id="mainwx">
<div class="fltlft">
<p align="center">
<a title="Percentage of Normal Precipitation for July 1, 2012 to June 30, 2014 (WRCC)" href="wxdata1314/wrcc_precip_ponJul12012Jun302014b.gif" rel="wximage"> <img border="0" alt="Percentage of Normal Precipitation for July 1, 2012 to June 30, 2014 (WRCC)" src="wxdata1314/wrcc_precip_ponJul12012Jun302014c.jpg" width="300" height="232" /> </a> <img alt="Click" src="http://www.sierraphotography.com/wxnotes/images/click.gif" width="16" height="34" />
<br />
<span class="fontxxsmall">Two-Year Percentage of Normal Precipitation<br />
July 1, 2012 to June 30, 2014 (WRCC). </span>
</p>
</div>
<p>
<span class="dropcap">D</span>owntown Los Angeles (USC) finished the water year (July
1 to June 30) with 6.08 inches of recorded rainfall. This is about 41% of the 1981-2010
normal of 14.93 inches. It was the seventh driest water year since recordkeeping began
in 1877. When combined with last year's water year total of 5.85 inches, the back-to-back
water years from July 1, 2012 to June 30, 2014 are the driest on record for Los Angeles.
The total rainfall deficit over the two year period was about 18 inches.
</p>
<p>
<span class="dropcap">E</span>l Nino has been knocking on the door, but until very
recently the atmosphere has only been responding in spits and sputters.
</p>
<p>
<span class="dropcap">T</span>he weekly <a href="http://www.cpc.ncep.noaa.gov/data/indices/wksst8110.for" target="_blank">OISST.v2
Nino 3.4 SST temperature anomaly</a> has been vacillating in the range 0.4 to 0.6
beginning with the week centered on April 23, 2014 and now stands at 0.5. Nino 1+2
and Nino 3 anomalies have generally been increasing and as of the week centered on
June 25 are at 1.6 and 1.0 respectively. Here is a <a href="wxdata1314/CPC_ElNinoRegionSSTAnom063014.gif" rel="wximage" target="_blank">plot
of the Nino regions SST anomalies</a> from the CPC. Following a period of strengthened
tradewinds, another westerly wind burst has developed in the Western Pacific. There
have been <a href="wxdata1314/CPC_CDAS850a062914b.gif" rel="wximage" target="_blank">several
WWB this year</a> and the most recent WWB could lead to additional warming of equatorial
SSTs.
</p>
<p>
<span class="dropcap">I</span>n response to the <a href="wxdata1314/CPC_tlon_heat_062714b.gif" rel="wximage" target="_blank">upwelling
phase of an oceanic Kelvin wave</a> there has been a <a href="wxdata1314/CPC_EqHeatContentAnom063014.gif" rel="wximage" target="_blank">decrease
in subsurface Pacific equatorial heat content</a> and some <a href="wxdata1314/CPC_EqTempDepth_062714b.gif" rel="wximage" target="_blank">associated
cooling at depth</a>.
</p>
<p>
<span class="dropcap">T</span>he <a href="http://www.esrl.noaa.gov/psd/map/clim/test_maproom.html" target="_blank">Global
Wind Oscillation</a> (GWO) can be a useful tool for evaluating the degree to which
the atmosphere is responding to El Nino or La Nina conditions. As this plot of the <a href="wxdata1314/gwo_030197_073197b.png" rel="wximage" target="_blank">GWO
for the period March 1 to July 31, 1997</a> shows, during the spring and summer of
1997 El Nino conditions were already resulting in a definitive atmospheric response.
Here is a plot of the <a href="wxdata1314/gwo_030114_070114b.png" rel="wximage" target="_blank">GWO
from March 1 to July 1 of this year</a>. Over most of this period the GWO has shown
a neutral or weak La Nina-like response. Recently the GWO has exhibited a positive
shift in AAM anomaly that, if sustained, could be indicative of a coupled ocean-atmosphere
response.
</p>
<p>
<span class="dropcap">T</span>he Plume-based and Consensus Forecasts in the <a href="wxdata1314/IRI_CPC_Quick_Look061914.pdf" target="_blank">June
19 IRI/CPC ENSO Quick Look</a> (PDF) show an increasing chance of El Nino conditions
developing over the NH summer, with an approximately 80% chance of El Nino conditions
being established by the OND season. A <a href="wxdata1314/CFSv2Nino34Anom070214b.gif" rel="wximage" target="_blank">July
2 run of the CFSv2</a> forecasts Nino 3.4 anomalies to briefly decline, then increase
substantially from July into October. We'll see!
</p>
<p>
<span class="dropcap">M</span>ore information about Southern California weather and
climate can be found using our <a href="weatherlinks.htm">WEATHER LINKS</a> page.
</p>
<p>
</p>
</div>
<img width="0" height="0" src="http://www.sierraphotography.com/wxnotes/aggbug.ashx?id=d3d30989-63e9-4c81-95ae-9bba8f08fbdd" />
<br />
<hr />Southern California Weather Notes Copyright 2000-2017 Gary Valle. All Rights Reserved.climateEl NinoGlobal Wind Oscillation (GWO)Los Angeles rainfallWesterly Wind Burst (WWB)http://www.sierraphotography.com/wxnotes/Trackback.aspx?guid=3ba1b048-64a6-4674-aabc-2ef1f4d56a3ahttp://www.sierraphotography.com/wxnotes/pingback.aspxhttp://www.sierraphotography.com/wxnotes/PermaLink,guid,3ba1b048-64a6-4674-aabc-2ef1f4d56a3a.aspxGary Valle

Beginning Wednesday evening (Feb 26) and continuing into
Sunday (Mar 2), the storm systems produced the most rain over five days in Los Angeles
since December 2010, ending a nearly 14 month period with record-setting dry weather.
Los Angeles experienced the driest calendar year on record in 2013, and until Friday
had recorded less water year rainfall than in 2006-07 — the driest water year (July
1 - June 30) since recordkeeping began in 1877.

According to preliminary precipitation data, Downtown
Los Angeles (USC) recorded 4.52 inches of rain over the course of the storms, increasing
its water year total from a dessicated 11% of normal to a not-too-bad-considering
50% of normal. Downtown Los Angeles' water year rain total now stands at 5.72 inches.
This exceeds last year's cumulative precipitation total on this date by more than
an inch, but still leaves us with a deficit of nearly six inches. The storms increased
February's rainfall total to near normal, and jump-started March with nearly half
its normal amount of rain. Prior to these storms the most rain recorded at Los Angeles
in a day this water year was 0.29 inch back in November!

With this recent rainfall 2013-14 will not be the driest
water year in Los Angeles, but one good storm, or even two, "does not a rain season
make." In the short term these storms have dramatically reduced the fire danger, provided
crucial relief to plants and animals, and increased groundwater and reservoir storage.
What happens in the longer term we'll just have to see. Over the next several days
a series of systems are forecast to produce additional rain from Central California
north into the PNW. While no rain is forecast in Southern California over the next
week or so, and the 8-14 day outlook is for below average precipitation, as long as
the Pacific weather pattern remains progressive there should be additional opportunities
for rain in the weeks ahead.

More information about Southern California weather and
climate can be found using our WEATHER LINKS page.

Southern California Weather Notes Copyright 2000-2017 Gary Valle. All Rights Reserved.
Combination of Pacific Storms Produce Most Rain in Five Days in Los Angeles Since December 2010. Record Dry Los Angeles Water Year Ends, But Long Term Drought Continues. El Nino Knocking More Loudly at Door.http://www.sierraphotography.com/wxnotes/PermaLink,guid,3ba1b048-64a6-4674-aabc-2ef1f4d56a3a.aspxhttp://www.sierraphotography.com/wxnotes/CombinationOfPacificStormsProduceMostRainInFiveDaysInLosAngelesSinceDecember2010RecordDryLosAngelesWaterYearEndsButLongTermDroughtContinuesElNinoKnockingMoreLoudlyAtDoor.aspx
Wed, 05 Mar 2014 20:26:55 GMT
<div id="mainwx">
<div class="fltlft">
<p align="center">
<a title="NRL Terra-MODIS Composite 02/26/2014 2150 GMT" href="wxdata1314/20140226.1030.Terra.modis.true1KM.NE_Pacificb.jpg" rel="wximage"> <img border="0" alt="NRL Terra-MODIS Composite 02/26/2014 2150 GMT" src="wxdata1314/20140226.1030.Terra.modis.true1KM.NE_Pacificc.jpg" width="300" height="225" /> </a> <img alt="Click" src="http://www.sierraphotography.com/wxnotes/images/click.gif" width="16" height="34" />
<br />
<span class="fontxxsmall">NRL Terra-MODIS Composite 02/26/2014 2150 GMT<br />
02/26-02/27 System Approaching Coast; 02/28-03/02 System West of 140W. </span>
</p>
</div>
<p>
<span class="dropcap">E</span>xtended by the active phase of the MJO, a strong Pacific
jet provided the impetus for <a href="wxdata1314/20140226.1030.Terra.modis.true1KM.NE_Pacificb.jpg" rel="wximage" target="_blank">two
Pacific storm systems</a> to <a href="wxdata1314/ucar_nam500_vrt_20140228_12zb.gif" rel="wximage" target="_blank">undercut
a persistent ridge</a> over the West Coast and bring much-needed rain to parched California.
</p>
<p>
<span class="dropcap">B</span>eginning Wednesday evening (Feb 26) and continuing into
Sunday (Mar 2), the storm systems produced the most rain over five days in Los Angeles
since December 2010, ending a nearly 14 month period with record-setting dry weather.
Los Angeles experienced the driest calendar year on record in 2013, and until Friday
had recorded less water year rainfall than in 2006-07 — the driest water year (July
1 - June 30) since recordkeeping began in 1877.
</p>
<p>
<span class="dropcap">A</span>ccording to preliminary precipitation data, Downtown
Los Angeles (USC) recorded 4.52 inches of rain over the course of the storms, increasing
its water year total from a dessicated 11% of normal to a not-too-bad-considering
50% of normal. Downtown Los Angeles' water year rain total now stands at 5.72 inches.
This exceeds last year's cumulative precipitation total on this date by more than
an inch, but still leaves us with a deficit of nearly six inches. The storms increased
February's rainfall total to near normal, and jump-started March with nearly half
its normal amount of rain. Prior to these storms the most rain recorded at Los Angeles
in a day this water year was 0.29 inch back in November!
</p>
<p>
<span class="dropcap">O</span>rographically favored foothill and mountain areas that
faced into the storms' moist southerly flow recorded some impressive rainfall totals.
According to this <a href="wxdata1314/RRMLOX030314_0500PST.pdf" target="_blank">compilation
of preliminary rainfall totals</a> from the NWS Los Angeles/Oxnard, Opids Camp near
Mt. Wilson recorded nearly 11 inches of rain, and several stations in the Ventura
Mountains recorded double-digit rainfall totals. Here are a <a href="wxdata1314/CNRFC7dayQPESoCal030314_12zb.jpg" rel="wximage" target="_blank">CNRFC
map of Gridded QPE</a> for the 7-day period ending March 3 at 4:00 am and a <a href="wxdata1314/CNRFC7dayQPE_RAW_4_SoCal030314_12zb.jpg" rel="wximage" target="_blank">CNRFC
map of 7-day Gridded QPE and 120 hr raw precipitation</a> for stations recording over
4.0 inches.
</p>
<p>
<span class="dropcap">W</span>ith this recent rainfall 2013-14 will not be the driest
water year in Los Angeles, but one good storm, or even two, "does not a rain season
make." In the short term these storms have dramatically reduced the fire danger, provided
crucial relief to plants and animals, and increased groundwater and reservoir storage.
What happens in the longer term we'll just have to see. Over the next several days
a series of systems are forecast to produce additional rain from Central California
north into the PNW. While no rain is forecast in Southern California over the next
week or so, and the 8-14 day outlook is for below average precipitation, as long as
the Pacific weather pattern remains progressive there should be additional opportunities
for rain in the weeks ahead.
</p>
<p>
<span class="dropcap">I</span>t looks like El Nino is beginning to knock more loudly
at the door. The third and strongest of a series of <a href="wxdata1314/EqUpperOceanHeatAnom022714b.gif" rel="wximage" target="_blank">oceanic
downwelling Kelvin waves</a> continues to significantly<a href="wxdata1314/CPC_wkxzteq_anm_022714b.gif" rel="wximage" target="_blank"> increase
subsurface equatorial heat content</a> in the Pacific basin and another <a href="wxdata1314/CDAS_850hPaU_Anom5N5S_030214b.gif" rel="wximage" target="_blank">strong
Westerly Wind Burst</a> has occurred in the equatorial Pacific. The <a href="wxdata1314/CFSv2nino34Mon030514b.gif" rel="wximage" target="_blank">CFSv2
forecasts Nino 3.4 anomalies</a> to reach El Nino thresholds in the May-June 2014
timeframe, however the <a href="wxdata1314/IRI_CPC_Quick_Look022014.pdf" target="_blank">IRI/CPC
Plume-based and Consensus Forecasts</a> released February 20 are less bullish, forecasting
about a 40% chance of El Nino conditions developing in the MJJ season. We'll see!
</p>
<p>
<span class="dropcap">M</span>ore information about Southern California weather and
climate can be found using our <a href="weatherlinks.htm">WEATHER LINKS</a> page.
</p>
<p>
</p>
</div>
<img width="0" height="0" src="http://www.sierraphotography.com/wxnotes/aggbug.ashx?id=3ba1b048-64a6-4674-aabc-2ef1f4d56a3a" />
<br />
<hr />Southern California Weather Notes Copyright 2000-2017 Gary Valle. All Rights Reserved.climateEl NinoLos Angeles rainfallMadden-Julian Oscillation (MJO)precipitation outlookweatherWesterly Wind Burst (WWB)http://www.sierraphotography.com/wxnotes/Trackback.aspx?guid=c991c6c4-7e34-44f2-ac22-69d0f1c87c8bhttp://www.sierraphotography.com/wxnotes/pingback.aspxhttp://www.sierraphotography.com/wxnotes/PermaLink,guid,c991c6c4-7e34-44f2-ac22-69d0f1c87c8b.aspxGary Valle

From July 1 to February 14 Downtown Los Angeles has recorded
only 1.20 inches of rain. This is less than the 1.92 inches of rainfall recorded over
the same period in 2006-2007, making 2013-2014 the driest water year to date since
recordkeeping began in July of 1877. Downtown Los Angeles averages 14.93 inches of
rain in a water year, July 1 through June 30.

Los Angeles recorded only a trace of rain in January,
and so far this February has recorded only 0.23 inch. At the moment neither the GFS
or ECMWF show any rain south of Pt. Conception through the morning of February 25.
At that time both models have another high amplitude ridge over the West Coast, so
unless something changes the chances for additional rain this month do not look good.
The 1981-2010 normal rainfall for January is 3.12 inches and for February 3.80 inches.

Active weather in Central California culminating in a strong
atmospheric river event February 8-9 produced double-digit
precipitation totals in the coastal mountains and Sierra. Over the 5-day period
ending Monday, February 10 at 3:15 pm precipitation totals as high as 23.51 inches
were observed. Since February 12 another atmospheric river has been feeding moisture
into Northern California and Oregon.

More information about Southern California weather and
climate can be found using our WEATHER LINKS page.

Southern California Weather Notes Copyright 2000-2017 Gary Valle. All Rights Reserved.
To Date Los Angeles Water Year Rainfall Less Than Driest Year on Record. Is El Nino Knocking at the Door? Atmospheric River Event Results in Double-Digit Precipitation Totals in Central California.http://www.sierraphotography.com/wxnotes/PermaLink,guid,c991c6c4-7e34-44f2-ac22-69d0f1c87c8b.aspxhttp://www.sierraphotography.com/wxnotes/ToDateLosAngelesWaterYearRainfallLessThanDriestYearOnRecordIsElNinoKnockingAtTheDoorAtmosphericRiverEventResultsInDoubleDigitPrecipitationTotalsInCentralCalifornia.aspx
Sat, 15 Feb 2014 22:42:24 GMT
<div id="mainwx">
<div class="fltlft">
<p align="center">
<a title="GFS Modeled Water Vapor Analysis 02/09/14 00z (ESRL/PSD)" href="wxdata1314/20140209_00_gfs_000.ARb.png" rel="wximage"> <img border="0" alt="GFS Modeled Water Vapor Analysis 02/09/14 00z (ESRL/PSD)" src="wxdata1314/20140209_00_gfs_000.ARc.png" width="300" height="225" /> </a> <img alt="Click" src="http://www.sierraphotography.com/wxnotes/images/click.gif" width="16" height="34" />
<br />
<span class="fontxxsmall">GFS Modeled Water Vapor Analysis 02/09/14 00z<br />
Automated Atmospheric River Detection (ESRL/PSD) </span>
</p>
</div>
<p>
<span class="dropcap">F</span>rom July 1 to February 14 Downtown Los Angeles has recorded
only 1.20 inches of rain. This is less than the 1.92 inches of rainfall recorded over
the same period in 2006-2007, making 2013-2014 the driest water year to date since
recordkeeping began in July of 1877. Downtown Los Angeles averages 14.93 inches of
rain in a water year, July 1 through June 30.
</p>
<p>
<span class="dropcap">L</span>os Angeles recorded only a trace of rain in January,
and so far this February has recorded only 0.23 inch. At the moment neither the GFS
or ECMWF show any rain south of Pt. Conception through the morning of February 25.
At that time both models have another high amplitude ridge over the West Coast, so
unless something changes the chances for additional rain this month do not look good.
The 1981-2010 normal rainfall for January is 3.12 inches and for February 3.80 inches.
</p>
<p>
<span class="dropcap">A</span>ctive weather in Central California culminating in a<a href="wxdata1314/20140209_00_gfs_000.ARb.png" rel="wximage" target="_blank"> strong
atmospheric river event</a> February 8-9 produced <a href="wxdata1314/CNRFC120hrPrecip021014_1515PSTb.jpg" rel="wximage" target="_blank">double-digit
precipitation totals</a> in the coastal mountains and Sierra. Over the 5-day period
ending Monday, February 10 at 3:15 pm precipitation totals as high as 23.51 inches
were observed. Since February 12 another atmospheric river has been feeding moisture
into Northern California and Oregon.
</p>
<p>
<span class="dropcap">I</span>t looks like El Nino will be knocking at the door in
the next 2-3 months and we'll have to see if the atmosphere and ocean respond. The
third and strongest of a <a href="wxdata1314/EqUpperOceanHeatAnom020714b.gif" rel="wximage" target="_blank">series
of oceanic downwelling Kelvin waves</a> is propagating into the Eastern Pacific and
is increasing subsurface equatorial heat content in the Pacific basin. The <a href="wxdata1314/CFSv2nino34Mon021414b.gif" rel="wximage" target="_blank">CFSv2
forecasts Nino 3.4 anomalies</a> to reach El Nino thresholds in May, however the <a href="wxdata1314/IRI_CPC_Quick_Look020614.pdf" target="_blank">IRI/CPC
Plume-based and Consensus Forecasts</a> are far less bullish, forecasting about a
30% chance of El Nino conditions in the AMJ season. We'll see!
</p>
<p>
<span class="dropcap">M</span>ore information about Southern California weather and
climate can be found using our <a href="weatherlinks.htm">WEATHER LINKS</a> page.
</p>
<p>
</p>
</div>
<img width="0" height="0" src="http://www.sierraphotography.com/wxnotes/aggbug.ashx?id=c991c6c4-7e34-44f2-ac22-69d0f1c87c8b" />
<br />
<hr />Southern California Weather Notes Copyright 2000-2017 Gary Valle. All Rights Reserved.climateEl NinoLos Angeles rainfallweatherhttp://www.sierraphotography.com/wxnotes/Trackback.aspx?guid=bef487c5-4159-40c7-98d4-02105bc42a0fhttp://www.sierraphotography.com/wxnotes/pingback.aspxhttp://www.sierraphotography.com/wxnotes/PermaLink,guid,bef487c5-4159-40c7-98d4-02105bc42a0f.aspxGary Valle

Downtown Los Angeles Rainfall
Driest Calendar Years 1878-2013.

Since January 1 Downtown Los Angeles has recorded only
3.60 inches of rain, making it the driest calendar year since recordkeeping began
in July of 1877. The previous record of 4.08 inches was set in 1953 and 1947. Downtown
Los Angeles averages about 15 inches of rain in a calendar year.

Precipitation composites for years with comparable PD0-AMO
indices constructed by Dr. Klaus Wolter of the Cooperative
Institute for Research in Environmental Sciences at the University of Colorado
appears to have anticipated this year's drought in Southern California. While Oct-Dec
anomalies for Southern California were -0.5 to -0.7 SD below the 1895-2000 Longterm
Average, Jan-Mar
anomalies were -0.1 to -0.3 SD below average. Assuming the anomaly maps to be
correlative the drought's stranglehold on Southern California may weaken somewhat
over the next three months.

To get an idea of how the precipitation anomaly might
vary over the next three months, the US Climate Division Dataset Mapping Page was
used to recreate the standardized Oct-Dec
precipitation anomaly and Jan-Mar
precipitation anomaly maps using the same years as Dr. Wolter's composites. Then
standardized composite precipitation anomaly maps were constructed for the months
of January, February,
and March.
Based on these composites some lessening of the severity of the drought in Southern
California is suggested throughout the period Jan-Mar with the biggest improvement
indicated in March -- except for coastal Southern California. A map showing the composite
precipitation anomaly in inches for the period October
to March was also generated.

While today's medium range forecasts and 6-10 day and
8-14 day precipitation outlooks aren't particularly encouraging there are some straws
to grasp. The AO
Index, which has been positive for most of the rainy season is now negative and
the Global Wind
Oscillation (GWO) is in its first full orbit into positive AAM territory in several
months. Whether these changes eventually result in rain for Southern California we'll
just have to see.

More information about Southern California weather and
climate can be found using our WEATHER LINKS page.

Southern California Weather Notes Copyright 2000-2017 Gary Valle. All Rights Reserved.
Driest Calendar Year in Los Angeles Since Recordkeeping Began in 1877. Composites Suggest Below Average Rainfall to Continue, But Some Lessening of the Drought in Southern California Possible.http://www.sierraphotography.com/wxnotes/PermaLink,guid,bef487c5-4159-40c7-98d4-02105bc42a0f.aspxhttp://www.sierraphotography.com/wxnotes/DriestCalendarYearInLosAngelesSinceRecordkeepingBeganIn1877CompositesSuggestBelowAverageRainfallToContinueButSomeLesseningOfTheDroughtInSouthernCaliforniaPossible.aspx
Wed, 01 Jan 2014 21:44:12 GMT
<div id="mainwx">
<div class="fltlft">
<p align="center">
<a title="Downtown Los Angeles Rainfall for the Driest Calendar Years from 1878-2013." href="wxdata1314/LA_DriestCY1878_2013b.png" rel="wximage"> <img border="0" alt="Downtown Los Angeles Rainfall for the Driest Calendar Years from 1878-2013." src="wxdata1314/LA_DriestCY1878_2013c.png" width="300" height="202" /> </a> <img alt="Click" src="http://www.sierraphotography.com/wxnotes/images/click.gif" width="16" height="34" />
<br />
<span class="fontxxsmall">Downtown Los Angeles Rainfall<br />
Driest Calendar Years 1878-2013.<br />
</span>
</p>
</div>
<p>
<span class="dropcap">S</span>ince January 1 Downtown Los Angeles has recorded only
3.60 inches of rain, making it the driest calendar year since recordkeeping began
in July of 1877. The previous record of 4.08 inches was set in 1953 and 1947. Downtown
Los Angeles averages about 15 inches of rain in a calendar year.
</p>
<p>
<span class="dropcap">P</span>recipitation composites for years with comparable PD0-AMO
indices constructed by Dr. Klaus Wolter of the <a href="http://cires.colorado.edu/index.html" target="_blank">Cooperative
Institute for Research in Environmental Sciences</a> at the University of Colorado
appears to have anticipated this year's drought in Southern California. While <a title="Prepared by Klaus Wolter, CIRES &amp; NOAA-ESRL PSD" href="wxdata1314/Wolter_PrecipCompOctDecPDOAMO2014b.jpg" rel="wximage" target="_blank">Oct-Dec
anomalies</a> for Southern California were -0.5 to -0.7 SD below the 1895-2000 Longterm
Average, <a title="Prepared by Klaus Wolter, CIRES &amp; NOAA-ESRL PSD" href="wxdata1314/Wolter_PrecipCompJanMarPDOAMO2014b.jpg" rel="wximage" target="_blank">Jan-Mar
anomalies</a> were -0.1 to -0.3 SD below average. Assuming the anomaly maps to be
correlative the drought's stranglehold on Southern California may weaken somewhat
over the next three months.
</p>
<p>
<span class="dropcap">T</span>o get an idea of how the precipitation anomaly might
vary over the next three months, the US Climate Division Dataset Mapping Page was
used to recreate the standardized <a href="wxdata1314/AfterWolter_PrecipCompOctDecPDOAMO2014b.png" rel="wximage" target="_blank">Oct-Dec
precipitation anomaly</a> and <a href="wxdata1314/AfterWolter_PrecipCompJanMarPDOAMO2014b.png" rel="wximage" target="_blank">Jan-Mar
precipitation anomaly</a> maps using the same years as Dr. Wolter's composites. Then
standardized composite precipitation anomaly maps were constructed for the months
of <a href="wxdata1314/AfterWolter_PrecipCompJanPDOAMO2014b.png" rel="wximage" target="_blank">January</a>, <a href="wxdata1314/AfterWolter_PrecipCompFebPDOAMO2014b.png" rel="wximage" target="_blank">February</a>,
and <a href="wxdata1314/AfterWolter_PrecipCompMarPDOAMO2014b.png" rel="wximage" target="_blank">March</a>.
Based on these composites some lessening of the severity of the drought in Southern
California is suggested throughout the period Jan-Mar with the biggest improvement
indicated in March -- except for coastal Southern California. A map showing the composite
precipitation anomaly in inches for the period <a href="wxdata1314/AfterWolter_PrecipCompOctDecInPDOAMO2014b.png" rel="wximage" target="_blank">October
to March</a> was also generated.
</p>
<p>
<span class="dropcap">W</span>hile today's medium range forecasts and 6-10 day and
8-14 day precipitation outlooks aren't particularly encouraging there are some straws
to grasp. The <a href="http://www.cpc.ncep.noaa.gov/products/precip/CWlink/daily_ao_index/ao.shtml" target="_blank">AO
Index,</a> which has been positive for most of the rainy season is now negative and
the <a href="wxdata1314/gwo_90d010114b.gif" rel="wximage" target="_blank">Global Wind
Oscillation</a> (GWO) is in its first full orbit into positive AAM territory in several
months. Whether these changes eventually result in rain for Southern California we'll
just have to see.
</p>
<p>
<span class="dropcap">M</span>ore information about Southern California weather and
climate can be found using our <a href="weatherlinks.htm">WEATHER LINKS</a> page.
</p>
<p>
</p>
</div>
<img width="0" height="0" src="http://www.sierraphotography.com/wxnotes/aggbug.ashx?id=bef487c5-4159-40c7-98d4-02105bc42a0f" />
<br />
<hr />Southern California Weather Notes Copyright 2000-2017 Gary Valle. All Rights Reserved.climateGlobal Wind Oscillation (GWO)Los Angeles rainfallprecipitation outlookweatherhttp://www.sierraphotography.com/wxnotes/Trackback.aspx?guid=688b8f60-47be-4c46-852c-2f7e85457e76http://www.sierraphotography.com/wxnotes/pingback.aspxhttp://www.sierraphotography.com/wxnotes/PermaLink,guid,688b8f60-47be-4c46-852c-2f7e85457e76.aspxGary Valle

According to Dr. Wolter the statistical forecast scheme
integrates as many of the known influences on California's climate as possible, using
data from 1950 onwards. In the absence of El Nino and La Nina influences considerations
such as the status of the Pacific Decadal Oscillation (PDO), the Atlantic Multidecadal
Oscillation (AMO), or recent Alaskan temperatures can be evaluated through statistical
models to make a forecast.

Dr. Wolter also produced composite precipitation anomalies
for the periods October-December and January-March for years with comparable PD0-AMO
indices. In Southern California the Oct-Dec
anomalies were -0.5 to -0.7 SD below the 1895-2000 Longterm Average and the Jan-Mar
anomalies were -0.1 to -0.3 SD below average.

Since October 1 precipitation
in California, Oregon and Washington has generally been well below normal. As
of today the precipitation recorded at Downtown Los Angeles is at about 30% of normal
for the water year (July 1-June30). If Los Angeles doesn't record more than 0.58 inch
of rain over the remainder of December, 2013 will rank as the driest calendar year
on record.

More information about Southern California weather and
climate can be found using our WEATHER LINKS page.

Southern California Weather Notes Copyright 2000-2017 Gary Valle. All Rights Reserved.
Experimental PSD Precipitation Outlook for California. Driest Calendar Year for Los Angeles in 135 Years? Atmospheric Rivers More Frequent When PNA and AO Negative.http://www.sierraphotography.com/wxnotes/PermaLink,guid,688b8f60-47be-4c46-852c-2f7e85457e76.aspxhttp://www.sierraphotography.com/wxnotes/ExperimentalPSDPrecipitationOutlookForCaliforniaDriestCalendarYearForLosAngelesIn135YearsAtmosphericRiversMoreFrequentWhenPNAAndAONegative.aspx
Sun, 15 Dec 2013 23:34:32 GMT
<div id="mainwx">
<div class="fltlft">
<p align="center">
<a title="Experimental PSD Precipitation Forecast Guidance, issued November 19, 2013. Prepared by Klaus Wolter, CIRES &amp; NOAA-ESRL PSD" href="wxdata1314/Wolter_ExpPSDPrecip111913b.jpg" rel="wximage"> <img border="0" alt="Experimental PSD Precipitation Forecast Guidance" src="wxdata1314/Wolter_ExpPSDPrecip111913c.jpg" width="275" height="356" /> </a> <img alt="Click" src="http://www.sierraphotography.com/wxnotes/images/click.gif" width="16" height="34" />
<br />
<span class="fontxxsmall">Experimental PSD Precipitation Forecast Guidance<br />
Issued November 19, 2013.<br />
Prepared by Klaus Wolter, CIRES &amp; NOAA-ESRL PSD</span>
</p>
</div>
<p>
<span class="dropcap">A</span>n <a title="Experimental PSD Precipitation Forecast Guidance, issued November 19, 2013. Prepared by Klaus Wolter, CIRES &amp; NOAA-ESRL PSD" href="wxdata1314/Wolter_ExpPSDPrecip111913b.jpg" rel="wximage" target="_blank">experimental
PSD forecast</a> issued November 19, 2013 for the period December 2013 through February
2014 <a href="http://www.water.ca.gov/news/newsreleases/2013/112513.pdf" target="_blank">prepared
for the California DWR</a> by Dr. Klaus Wolter of the <a href="http://cires.colorado.edu/index.html" target="_blank">Cooperative
Institute for Research in Environmental Sciences</a> at the University of Colorado
shows a significantly increased chance of less than normal precipitation in most of
Southern California and the Central San Joaquin Valley. The forecast guidance shows
the shift in tercile probabilities for precipitation, similar in concept to the <a href="http://www.cpc.ncep.noaa.gov/products/predictions/90day/" target="_blank">NOAA
CPC precipitation outlooks</a>.
</p>
<p>
<span class="dropcap">A</span>ccording to Dr. Wolter the statistical forecast scheme
integrates as many of the known influences on California's climate as possible, using
data from 1950 onwards. In the absence of El Nino and La Nina influences considerations
such as the status of the Pacific Decadal Oscillation (PDO), the Atlantic Multidecadal
Oscillation (AMO), or recent Alaskan temperatures can be evaluated through statistical
models to make a forecast.
</p>
<p>
<span class="dropcap">D</span>r. Wolter also produced composite precipitation anomalies
for the periods October-December and January-March for years with comparable PD0-AMO
indices. In Southern California the <a title="Prepared by Klaus Wolter, CIRES &amp; NOAA-ESRL PSD" href="wxdata1314/Wolter_PrecipCompOctDecPDOAMO2014b.jpg" rel="wximage" target="_blank">Oct-Dec
anomalies</a> were -0.5 to -0.7 SD below the 1895-2000 Longterm Average and the <a title="Prepared by Klaus Wolter, CIRES &amp; NOAA-ESRL PSD" href="wxdata1314/Wolter_PrecipCompJanMarPDOAMO2014b.jpg" rel="wximage" target="_blank">Jan-Mar
anomalies</a> were -0.1 to -0.3 SD below average.
</p>
<p>
<span class="dropcap">S</span>ince October 1 <a href="wxdata1314/wrcc_precip_ponOct1Dec142013b.gif" rel="wximage" target="_blank">precipitation
in California, Oregon and Washington</a> has generally been well below normal. As
of today the precipitation recorded at Downtown Los Angeles is at about 30% of normal
for the water year (July 1-June30). If Los Angeles doesn't record more than 0.58 inch
of rain over the remainder of December, 2013 will rank as the driest calendar year
on record.
</p>
<p>
<span class="dropcap">A</span> wildcard in the California precipitation outlook is
the occurrence of atmospheric rivers such as those that occurred at the <a href="http://www.sierraphotography.com/wxnotes/NovemberAAMHighestSinceElNinoOf200910AtmosphericRiversProduceHeavyPrecipitationInCentralAndNorthernCalifornia.aspx" target="_blank">end
of November 2012</a> and during <a href="http://www.sierraphotography.com/wxnotes/default,month,2010-12.aspx" target="_blank">December
2010</a>. An analysis of all winter ARs in California during WY1998–2011 presented
in the paper <i><a href="http://onlinelibrary.wiley.com/doi/10.1002/wrcr.20537/abstract" target="_blank">The
2010/2011 snow season in California's Sierra Nevada: Role of atmospheric rivers and
modes of large-scale variability</a></i> by Bin Guan, et.al., found that atmospheric
river frequency is increased during negative phases of the <a href="http://www.cpc.ncep.noaa.gov/products/precip/CWlink/daily_ao_index/ao.shtml" target="_blank">Arctic
Oscillation</a> (AO) and the <a href="http://www.cpc.ncep.noaa.gov/products/precip/CWlink/pna/pna.shtml" target="_blank">Pacific-North
American</a> (PNA) teleconnection patterns.
</p>
<p>
<span class="dropcap">M</span>ore information about Southern California weather and
climate can be found using our <a href="weatherlinks.htm">WEATHER LINKS</a> page.
</p>
<p>
</p>
</div>
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<br />
<hr />Southern California Weather Notes Copyright 2000-2017 Gary Valle. All Rights Reserved.climateLos Angeles rainfallprecipitation outlookrecord rainfallweatherhttp://www.sierraphotography.com/wxnotes/Trackback.aspx?guid=880b72b1-8553-467a-8cb0-ccaa8254f34bhttp://www.sierraphotography.com/wxnotes/pingback.aspxhttp://www.sierraphotography.com/wxnotes/PermaLink,guid,880b72b1-8553-467a-8cb0-ccaa8254f34b.aspxGary Valle

CPC Dec-Jan-Feb Precipitation Outlook
Released October 17, 2013.

Updated November 5, 2013. My mistake -- a spreadsheet range error -- thanks
for the heads up Reg! The driest January 1 to November 1 for Downtown Los Angeles
was in 1972 with 0.92 inch. Here are the driest ten years for that period:

An energetic
upper level low brought the first widespread precipitation of the rain season
to Southern California October 9, with rain at the lower elevations and some snow
in the local mountains. Rainfall
amounts varied widely, ranging from a trace in some areas to over an inch in the
mountains.

Downtown Los Angeles (USC) recorded only 0.04 inch for
the storm, bringing the water year rainfall total to 0.13 inch, which is 0.31 inch
below normal. Downtown Los Angeles has recorded only 2.76 inches of rain since January
1. This is one of the driest January 1 - October 20 in Los Angeles over the past 135
years! To get out of the bottom ten for calendar year rainfall Los Angeles needs about
3.5 inches of rain by December 31. Normal rainfall for November is 1.04 inches and
for December is 2.33 inches.

For months I've been monitoring climate data and forecasts
looking for something on which to base a 2013-14 Winter precipitation Outlook. Historically
ENSO has played the major role in Southern California rain season weather, with El
Nino conditions generally producing wetter weather and La Nina conditions generally
drier. But ENSO conditions are currently Neutral and are expected to remain so through
the end of the year.

Most climate models forecast
slow warming of SSTs in the equatorial Pacific (NINO 3.4 region) over the next
several months, but at this time of the year it would be very unusual to have substantial
warming. The CPC/IRI
ENSO Forecasts from IRI's October Quick Look indicate the probability of an El
Nino developing before the end of the year is less than 20% -- and 20% seems high.

One computer model that at times has been forecasting
above average precipitation in Southern California this Winter is the Climate Forecast
System version 2 (CFSv2). The CFSv2 is fully coupled ocean-atmosphere-land-sea ice
model used to forecast parameters such as sea surface temperature, temperature and
precipitation rate. While skillful at predicting tropical SSTs, the CFSv2 generally
performs very poorly when forecasting precipitation over land, so forecasts such as
this earlier
one for Dec-Jan-Feb must be viewed somewhat skeptically.

Another glass half-full observation is that the Madden-Julian
Oscillation (MJO) has been relatively active this year and if this activity continues
it provides recurring opportunities for enhanced U.S. West Coast precipitation. The
downside is that it can result in periods of dry weather as well.

With the ocean and atmosphere neutral there's just not
much on which to base a rain season forecast. As a result of the government shutdown
the release of the official NOAA 2013-14 Winter Outlook has been delayed until November.
The October CPC outlook is usually the basis of the initial official NOAA U.S. Winter
Outlook. The U.S.
Dec-Jan-Feb Precipitation Outlook, released October 17, calls for an equal chance
of below average, average, or above average precipitation for all of California. We'll
see!

More information about Southern California weather and
climate can be found using our WEATHER LINKS page.

Southern California Weather Notes Copyright 2000-2017 Gary Valle. All Rights Reserved.
First Widespread Precipitation of the Rain Season. One of the Driest Calendar Years for Los Angeles in 135 Years! Southern California 2013-14 Winter Precipitation Outlook.http://www.sierraphotography.com/wxnotes/PermaLink,guid,880b72b1-8553-467a-8cb0-ccaa8254f34b.aspxhttp://www.sierraphotography.com/wxnotes/FirstWidespreadPrecipitationOfTheRainSeasonOneOfTheDriestCalendarYearsForLosAngelesIn135YearsSouthernCalifornia201314WinterPrecipitationOutlook.aspx
Sun, 20 Oct 2013 22:31:26 GMT
<div id="mainwx">
<div class="fltlft">
<p align="center">
<a title="CPC Dec-Jan-Feb Precipitation Outlook, released October 17, 2013." href="wxdata1314/cpc_precipDJF101713b.gif" rel="wximage"> <img border="0" alt="CPC Dec-Jan-Feb Precipitation Outlook" src="wxdata1314/cpc_precipDJF101713c.gif" width="300" height="279" /> </a> <img alt="Click" src="http://www.sierraphotography.com/wxnotes/images/click.gif" width="16" height="34" />
<br />
<span class="fontxxsmall">CPC Dec-Jan-Feb Precipitation Outlook<br />
Released October 17, 2013.</span>
</p>
</div>
<p>
<i>Updated November 5, 2013</i>. My mistake -- a spreadsheet range error -- thanks
for the heads up Reg! The driest January 1 to November 1 for Downtown Los Angeles
was in 1972 with 0.92 inch. Here are the driest ten years for that period:
</p>
<p>
1. 1972 0.92<br />
2. 2002 1.62<br />
3. 1984 1.93<br />
4. 1961 2.37<br />
5. 1971 2.39<br />
6. 1947 2.45<br />
7. 2013 2.78<br />
8. 1894 2.89<br />
9. 1953 2.89<br />
10. 2007 3.37<br />
</p>
<p>
<span class="dropcap">A</span>n <a href="wxdata1314/goes15wv100913_2100zb.gif" rel="wximage" target="_blank">energetic
upper level low</a> brought the first widespread precipitation of the rain season
to Southern California October 9, with rain at the lower elevations and some snow
in the local mountains. <a href="wxdata1314/RRMLOX101013_0305PDT.pdf" target="_blank">Rainfall
amounts varied widely</a>, ranging from a trace in some areas to over an inch in the
mountains.
</p>
<p>
<span class="dropcap">D</span>owntown Los Angeles (USC) recorded only 0.04 inch for
the storm, bringing the water year rainfall total to 0.13 inch, which is 0.31 inch
below normal. Downtown Los Angeles has recorded only 2.76 inches of rain since January
1. This is one of the driest January 1 - October 20 in Los Angeles over the past 135
years! To get out of the bottom ten for calendar year rainfall Los Angeles needs about
3.5 inches of rain by December 31. Normal rainfall for November is 1.04 inches and
for December is 2.33 inches.
</p>
<p>
<span class="dropcap">F</span>or months I've been monitoring climate data and forecasts
looking for something on which to base a 2013-14 Winter precipitation Outlook. Historically
ENSO has played the major role in Southern California rain season weather, with El
Nino conditions generally producing wetter weather and La Nina conditions generally
drier. But ENSO conditions are currently Neutral and are expected to remain so through
the end of the year.
</p>
<p>
<span class="dropcap">M</span>ost climate models <a href="wxdata1314/IRI_CPC_PredPlume091813b.gif" rel="wximage" target="_blank">forecast
slow warming of SSTs</a> in the equatorial Pacific (NINO 3.4 region) over the next
several months, but at this time of the year it would be very unusual to have substantial
warming. The <a href="wxdata1314/CPC_IRI_Consensus101013b.gif" rel="wximage" target="_blank">CPC/IRI
ENSO Forecasts</a> from IRI's October Quick Look indicate the probability of an El
Nino developing before the end of the year is less than 20% -- and 20% seems high.
</p>
<p>
<span class="dropcap">O</span>ne computer model that at times has been forecasting
above average precipitation in Southern California this Winter is the Climate Forecast
System version 2 (CFSv2). The CFSv2 is fully coupled ocean-atmosphere-land-sea ice
model used to forecast parameters such as sea surface temperature, temperature and
precipitation rate. While skillful at predicting tropical SSTs, the CFSv2 generally
performs very poorly when forecasting precipitation over land, so forecasts such as
this <a href="wxdata1314/usPrecSeaMaskDJF_100313_101213b.gif" rel="wximage" target="_blank">earlier
one for Dec-Jan-Feb</a> must be viewed somewhat skeptically.
</p>
<p>
<span class="dropcap">A</span>nother glass half-full observation is that the Madden-Julian
Oscillation (MJO) has been relatively active this year and if this activity continues
it provides recurring opportunities for enhanced U.S. West Coast precipitation. The
downside is that it can result in periods of dry weather as well.
</p>
<p>
<span class="dropcap">W</span>ith the ocean and atmosphere neutral there's just not
much on which to base a rain season forecast. As a result of the government shutdown
the release of the official NOAA 2013-14 Winter Outlook has been delayed until November.
The October CPC outlook is usually the basis of the initial official NOAA U.S. Winter
Outlook. The <a href="wxdata1314/cpc_precipDJF101713b.gif" rel="wximage" target="_blank">U.S.
Dec-Jan-Feb Precipitation Outlook</a>, released October 17, calls for an equal chance
of below average, average, or above average precipitation for all of California. We'll
see!
</p>
<p>
<span class="dropcap">M</span>ore information about Southern California weather and
climate can be found using our <a href="weatherlinks.htm">WEATHER LINKS</a> page.
</p>
<div class="clearfloat">
</div>
</div>
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<br />
<hr />Southern California Weather Notes Copyright 2000-2017 Gary Valle. All Rights Reserved.climateEl NinoGlobal Wind Oscillation (GWO)La NinaLos Angeles rainfallMadden-Julian Oscillation (MJO)precipitation outlookrecord rainfallSierra snowpackweatherhttp://www.sierraphotography.com/wxnotes/Trackback.aspx?guid=f091431a-dc89-4f83-b534-bdfa02a5030bhttp://www.sierraphotography.com/wxnotes/pingback.aspxhttp://www.sierraphotography.com/wxnotes/PermaLink,guid,f091431a-dc89-4f83-b534-bdfa02a5030b.aspxGary Valle

Western U.S. Precipitation - Percent of Average (WRCC)
July 1, 2012 to June 30, 2013.

Downtown Los Angeles (USC) finished the water year (July
1 to June 30) with only 5.85 inches of recorded rainfall, making it the sixth driest
water year since recordkeeping began in 1877. With a deficit of over 9 inches, the
water year rainfall total was about 39% of the norm of 14.93 inches. This tabulation
of Rain
Season Totals from the NWS/Oxnard shows rainfall totals around the area ranged
from a low of 14% of normal at Palmdale Airport to a high of 54% at Long Beach Airport
and LAX.

As this WRCC precipitation
map for the period July 1 to June 30 shows, below average precipitation was not
limited to Southern California. If it were not for heavy precipitation related to
atmospheric river events in late November/early December there would be even more
red on the map.

It has been even
drier since January 1. For example, since January 1 Downtown Los Angeles has received
only 25% of normal rainfall; Burbank 21% of normal; LAX 30% of normal; Santa Barbara
28% of normal; and Palmdale 19% of normal. Surprisingly, rainfall totals for Los Angeles
since January 1 are only the ninth driest on record. The driest January-June on record
was 1972 when 0.26 inch was recorded. And guess what -- we went on to have a very
wet rain season in 1972-73 with 21.26 inches of rain in Los Angeles!

As dry as it's been in the Los Angeles area since the
first of the year, it has been drier at some locations in the San Francisco Bay Area.
Remarkably, LAX has had more rain than SFO, and Burbank Airport in the San Fernando
Valley has had more rain than Napa Airport in the Napa Valley!

More information about Southern California weather and
climate can be found using our WEATHER LINKS page.

Southern California Weather Notes Copyright 2000-2017 Gary Valle. All Rights Reserved.
Los Angeles Water Year Rainfall Sixth Driest on Record. Paltry Year-to-Date Western U.S. Precipitation. LAX Leads SFO at the Half! http://www.sierraphotography.com/wxnotes/PermaLink,guid,f091431a-dc89-4f83-b534-bdfa02a5030b.aspxhttp://www.sierraphotography.com/wxnotes/LosAngelesWaterYearRainfallSixthDriestOnRecordPaltryYeartoDateWesternUSPrecipitationLAXLeadsSFOAtTheHalf.aspx
Mon, 01 Jul 2013 22:09:39 GMT
<div id="mainwx">
<div class="fltlft">
<p align="center">
<a title="Western U.S. Precipitation - Percent of Average (WRCC) for July 1, 2012 to June 30, 2013." href="wxdata1213/wrcc_pon_jul1jun30_2013b.png" rel="wximage"> <img border="0" alt="Western U.S. Precipitation - Percent of Average (WRCC) for July 1, 2012 to June 30, 2013." src="wxdata1213/wrcc_pon_jul1jun30_2013c.png" width="300" height="232" /> </a> <img alt="Click" src="http://www.sierraphotography.com/wxnotes/images/click.gif" width="16" height="34" />
<br />
<span class="fontxxsmall">Western U.S. Precipitation - Percent of Average (WRCC)<br />
July 1, 2012 to June 30, 2013.</span>
</p>
</div>
<p>
<span class="dropcap">D</span>owntown Los Angeles (USC) finished the water year (July
1 to June 30) with only 5.85 inches of recorded rainfall, making it the sixth driest
water year since recordkeeping began in 1877. With a deficit of over 9 inches, the
water year rainfall total was about 39% of the norm of 14.93 inches. This tabulation
of <a href="wxdata1213/NWS_WYTotals_2012-2013.jpg" rel="wximage" target="_blank">Rain
Season Totals from the NWS/Oxnard</a> shows rainfall totals around the area ranged
from a low of 14% of normal at Palmdale Airport to a high of 54% at Long Beach Airport
and LAX.
</p>
<p>
<span class="dropcap">A</span>s this WRCC <a href="wxdata1213/wrcc_pon_jul1jun30_2013b.png" rel="wximage" target="_blank">precipitation
map for the period July 1 to June 30</a> shows, below average precipitation was not
limited to Southern California. If it were not for heavy precipitation related to
atmospheric river events in late November/early December there would be even more
red on the map.
</p>
<p>
<span class="dropcap">I</span>t has been <a href="wxdata1213/wrcc_pon_jan1jun30_2013b.png" rel="wximage" target="_blank">even
drier since January 1</a>. For example, since January 1 Downtown Los Angeles has received
only 25% of normal rainfall; Burbank 21% of normal; LAX 30% of normal; Santa Barbara
28% of normal; and Palmdale 19% of normal. Surprisingly, rainfall totals for Los Angeles
since January 1 are only the ninth driest on record. The driest January-June on record
was 1972 when 0.26 inch was recorded. And guess what -- we went on to have a very
wet rain season in 1972-73 with 21.26 inches of rain in Los Angeles!
</p>
<p>
<span class="dropcap">A</span>s dry as it's been in the Los Angeles area since the
first of the year, it has been drier at some locations in the San Francisco Bay Area.
Remarkably, LAX has had more rain than SFO, and Burbank Airport in the San Fernando
Valley has had more rain than Napa Airport in the Napa Valley!
</p>
<p>
<span class="dropcap">M</span>ore information about Southern California weather and
climate can be found using our <a href="weatherlinks.htm">WEATHER LINKS</a> page.
</p>
<div class="clearfloat">
</div>
</div>
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<br />
<hr />Southern California Weather Notes Copyright 2000-2017 Gary Valle. All Rights Reserved.Los Angeles rainfallweatherhttp://www.sierraphotography.com/wxnotes/Trackback.aspx?guid=03d68b8e-678a-49be-b3f6-107408529808http://www.sierraphotography.com/wxnotes/pingback.aspxhttp://www.sierraphotography.com/wxnotes/PermaLink,guid,03d68b8e-678a-49be-b3f6-107408529808.aspxGary Valle

MIRS IWV All Satellites
December 2, 2012 1800 UTC Preceding 12 hours.

If you were to only look at the Global
Wind Oscillation (GWO) for November you might think our 2012-2013 El Nino hadn't
flopped. The relative AAM anomaly peaked at about 1.4 around November 20, which is
the highest it's been since the El Nino of 2009-2010.

Most of the AAM was added in the NH between
15°N and 30°N. This led to the development of a high amplitude mid-Pacific ridge,
and undercutting of the ridge by the westerlies. This enabled a low near the dateline
to tap tropical moisture and relay
it into the circulation of a large eastern Pacific low. This linkage provided
the moisture necessary to create the atmospheric rivers that produced excessive precipitation
in Northern and Central California last week.

Over the 5-day period ending Monday morning (December
3) Northern and Central California recorded double-digit precipitation totals with
several stations recording rainfall amounts in excess of 15 inches. Here are archived
Public Information Statements issued by NWS
San Francisco Bay Area/Monterey and NWS
Eureka with some of the phenomenal precipitation totals recorded in those areas.
This AHPS
Precipitation Analysis shows the observed precipitation in the western U.S. for
the 7-day period ending Monday morning.

New forecast methods developed by NOAA's
ESRL PSD using satellite-derived and GFS medium range forecast data indicated
high levels of water vapor transport early
Friday and early
Sunday. This typically characterizes AR events. This Evaluation
of GFS Forecast Fields (PDF) shows the observed Integrated Water Vapor (IWV) for
December 2, the corresponding analysis, and the 1-day to 5-day forecasts.

System dynamics were much weaker in Southern California,
and the IWV content of the atmospheric rivers was less. (Friday
IPW and Sunday
IPW). Even so orographically favored areas were still able to wring several inches
of rain from the moist flow. From Tuesday night to Monday morning Opids Camp recorded
3.02 inches, White Ledge Peak 4.09 inches, Refugio Pass 4.61 inches, and Rocky Butte
8.51 inches.

Over the same period Downtown Los Angeles (USC) recorded
1.03 inches, bringing the water year total to 1.36 inches. As of today that's 1.08
inch less than normal. Here's an archived copy of a NWS
compilation of preliminary rainfall totals in our area.

More information about Southern California weather and
climate can be found using our WEATHER LINKS page.

Southern California Weather Notes Copyright 2000-2017 Gary Valle. All Rights Reserved.
November AAM Highest Since El Nino of 2009-10. Atmospheric Rivers Produce Heavy Precipitation in Central and Northern California.http://www.sierraphotography.com/wxnotes/PermaLink,guid,03d68b8e-678a-49be-b3f6-107408529808.aspxhttp://www.sierraphotography.com/wxnotes/NovemberAAMHighestSinceElNinoOf200910AtmosphericRiversProduceHeavyPrecipitationInCentralAndNorthernCalifornia.aspx
Sun, 09 Dec 2012 01:30:17 GMT
<div id="mainwx">
<div class="fltlft">
<p align="center">
<a title="MIRS Integrated Water Vapor, December 2, 2012 1800 UTC for the preceeding 12 hours." href="http://www.sierraphotography.com/wxnotes/wxdata1213/12337_18utc_12h-ave_iwv_mirs_ALL.png" rel="wximage"> <img border="0" alt="MIRS Integrated Water Vapor, December 2, 2012 1800 UTC for the preceeding 12 hours." src="http://www.sierraphotography.com/wxnotes/wxdata1213/12337_18utc_12h-ave_iwv_mirs_ALLc.png" width="300" height="225" /> </a> <img alt="Click" src="http://www.sierraphotography.com/wxnotes/images/click.gif" width="16" height="34" />
<br />
<span class="fontxxsmall">MIRS IWV All Satellites<br />
December 2, 2012 1800 UTC Preceding 12 hours.</span>
</p>
</div>
<p>
<span class="dropcap">I</span>f you were to only look at the <a href="http://www.sierraphotography.com/wxnotes/wxdata1213/gwo_110112_120512b.png" rel="wximage" target="_blank">Global
Wind Oscillation (GWO) for November</a> you might think our 2012-2013 El Nino hadn't
flopped. The relative AAM anomaly peaked at about 1.4 around November 20, which is
the highest it's been since the El Nino of 2009-2010.
</p>
<p>
<span class="dropcap">M</span>ost of the AAM was added in the NH <a href="http://www.sierraphotography.com/wxnotes/wxdata1213/ESRL_PSDglaam.sig.90day120512b.gif" rel="wximage" target="_blank">between
15°N and 30°N</a>. This led to the development of a high amplitude mid-Pacific ridge,
and undercutting of the ridge by the westerlies. This enabled a low near the dateline
to tap tropical moisture and <a href="http://www.sierraphotography.com/wxnotes/wxdata1213/GFS_700pw_npac_113012_12zb.gif" rel="wximage" target="_blank">relay
it into the circulation of a large eastern Pacific low</a>. This linkage provided
the moisture necessary to create the atmospheric rivers that produced excessive precipitation
in Northern and Central California last week.
</p>
<p>
<span class="dropcap">O</span>ver the 5-day period ending Monday morning (December
3) Northern and Central California recorded double-digit precipitation totals with
several stations recording rainfall amounts in excess of 15 inches. Here are archived
Public Information Statements issued by <a href="http://www.sierraphotography.com/wxnotes/wxdata1213/PNSMTR120312_1101PST.pdf" target="_blank">NWS
San Francisco Bay Area/Monterey</a> and <a href="http://www.sierraphotography.com/wxnotes/wxdata1213/PNSEKA120312_1230PST.pdf" target="_blank">NWS
Eureka</a> with some of the phenomenal precipitation totals recorded in those areas.
This <a href="http://www.sierraphotography.com/wxnotes/wxdata1213/AHPS7dayPrecipWest120312_12zb.jpg" rel="wximage" target="_blank">AHPS
Precipitation Analysis</a> shows the observed precipitation in the western U.S. for
the 7-day period ending Monday morning.
</p>
<p>
<span class="dropcap">N</span>ew forecast methods developed by <a href="http://www.esrl.noaa.gov/psd/psd2/coastal/satres/ar_detect.html" target="_blank">NOAA's
ESRL PSD</a> using satellite-derived and GFS medium range forecast data indicated
high levels of water vapor transport <a href="http://www.sierraphotography.com/wxnotes/wxdata1213/20121129_12_gfs_024_xport.AR.png" rel="wximage" target="_blank">early
Friday</a> and <a href="http://www.sierraphotography.com/wxnotes/wxdata1213/20121129_12_gfs_072_xport.AR.png" rel="wximage">early
Sunday</a>. This typically characterizes AR events. This <a href="http://www.sierraphotography.com/wxnotes/wxdata1213/ESRL_PSD_ARDetectionEval120212.pdf" target="_blank">Evaluation
of GFS Forecast Fields</a> (PDF) shows the observed Integrated Water Vapor (IWV) for
December 2, the corresponding analysis, and the 1-day to 5-day forecasts.
</p>
<p>
<span class="dropcap">S</span>ystem dynamics were much weaker in Southern California,
and the IWV content of the atmospheric rivers was less. (<a href="http://www.sierraphotography.com/wxnotes/wxdata1213/SSMIS_IWV_12336.am.AR.120112b.png" rel="wximage" target="_blank">Friday
IPW</a> and <a href="http://www.sierraphotography.com/wxnotes/wxdata1213/SSMIS_IWV_12338.am.AR.120312b.png" rel="wximage" target="_blank">Sunday
IPW</a>). Even so orographically favored areas were still able to wring several inches
of rain from the moist flow. From Tuesday night to Monday morning Opids Camp recorded
3.02 inches, White Ledge Peak 4.09 inches, Refugio Pass 4.61 inches, and Rocky Butte
8.51 inches.
</p>
<p>
<span class="dropcap">O</span>ver the same period Downtown Los Angeles (USC) recorded
1.03 inches, bringing the water year total to 1.36 inches. As of today that's 1.08
inch less than normal. Here's an archived copy of a <a href="http://www.sierraphotography.com/wxnotes/wxdata1213/RRMLOX120312_1715PST.pdf" target="_blank">NWS
compilation of preliminary rainfall totals</a> in our area.
</p>
<p>
<span class="dropcap">M</span>ore information about Southern California weather and
climate can be found using our <a href="weatherlinks.htm">WEATHER LINKS</a> page.
</p>
<div class="clearfloat">
</div>
</div>
<img width="0" height="0" src="http://www.sierraphotography.com/wxnotes/aggbug.ashx?id=03d68b8e-678a-49be-b3f6-107408529808" />
<br />
<hr />Southern California Weather Notes Copyright 2000-2017 Gary Valle. All Rights Reserved.El NinoGlobal Wind Oscillation (GWO)Los Angeles rainfallweatherhttp://www.sierraphotography.com/wxnotes/Trackback.aspx?guid=9066c1f0-55c9-44dc-a264-76e36d91a6abhttp://www.sierraphotography.com/wxnotes/pingback.aspxhttp://www.sierraphotography.com/wxnotes/PermaLink,guid,9066c1f0-55c9-44dc-a264-76e36d91a6ab.aspxGary Valle

According to NWS Storm Reports a spotter in Simi Valley
area near Tapo St. and the 118 Frwy reported 1.0 inch of rain in 15 minutes and 1.5
inches in 30 minutes with street flooding. A Mesonet station in Simi Valley recorded
0.84 inches of rain in 12 minutes. A Mesonet station near Pasadena recorded 1.1 inches
in 25 minutes. Long Beach Airport set a new rainfall record for the date of 0.30 inches.

Downtown Los Angeles (USC) will end the the 2011-2012
water year (July 1 to June 30) having recorded 8.69 inches of rain. This is about
58% of the 1981-2010 normal of 14.93 inches. The deficit of 6.24 inches is a little
more than the 5-6 inch deficit recorded in a selection
of similar second year La Nina years. According to data compiled by the NWS Santa
Barbara will end the water year at about 66% of normal; Camarillo/Oxnard at 57%; Burbank
Airport at 51%; LAX at 59%; and Long Beach Airport at 62%.

This TAO/Triton plot of Pacific equatorial SST and anomaly
clearly depicts the evolution of our two year La Nina and the recent transition to
warmer conditions. Is an El Nino in the works for this Winter? According to the Multivariate
ENSO Index (MEI) a transition to El Nino conditions may already be underway. The
April/May value of the MEI was +0.706. This is already within the range of a weak
El Niño ranking. In his June 6 discussion of the MEI climatologist Klaus Wolter noted
the last month's increase in the MEI was the 6th highest increase for this time of
year since 1950. He also pointed out that it was the 4th monthly increase of this
caliber in a row -- second only to the record of six consecutive large monthly increases
in 1997 at the beginning of the mega El Nino of 1997-98. It will be very interesting
to see if the string of large increases in the MEI continues with the May/June value.

While the ocean seems to be on board with the El Nino
idea, the atmosphere appears to be balking -- at least for the moment. As of June
24, the
AAM component of the GWO was down around -2.0, which is nearly as low as it's
been during year two of the 2010-2012 La Nina. A positive value of AAM is generally
associated with El Nino conditions.

More information about Southern California weather and
climate can be found using our WEATHER LINKS page.

Southern California Weather Notes Copyright 2000-2017 Gary Valle. All Rights Reserved.
Downtown Los Angeles Ends 2011-2012 Water Year Six Inches Below Normal Rainfall. Is an El Nino in the Works for This Winter?http://www.sierraphotography.com/wxnotes/PermaLink,guid,a3e52768-20db-4c98-a8ea-206305ba9b2b.aspxhttp://www.sierraphotography.com/wxnotes/DowntownLosAngelesEnds20112012WaterYearSixInchesBelowNormalRainfallIsAnElNinoInTheWorksForThisWinter.aspx
Sat, 30 Jun 2012 23:27:44 GMT
<div id="mainwx">
<div class="fltlft">
<p align="center">
<a title="TAO/TRITON Time-Longitude Plot Pacific Equatorial SST and Anomaly - Saturday, June 30, 2012" href="wxdata1112/time_lon_EQ_hf_sst_sst_mean_anom_201006_201206_2012063013.gif" rel="wximage" target="_blank"> <img border="0" alt="TAO/TRITON Time-Longitude Plot SST and Anomaly" src="wxdata1112/time_lon_EQ_hf_sst_sst_mean_anom_201006_201206_2012063013c.gif" width="350" height="252" /> </a> <img alt="Click" src="images/click.gif" width="16" height="34" />
<br />
<span class="fontxxsmall">TAO/TRITON Time-Longitude Plot of SST and Anomaly<br />
Saturday, June 30, 2012</span>
</p>
</div>
<p>
<span class="dropcap">D</span>owntown Los Angeles (USC) will end the the 2011-2012
water year (July 1 to June 30) having recorded 8.69 inches of rain. This is about
58% of the 1981-2010 normal of 14.93 inches. The deficit of 6.24 inches is a little
more than the 5-6 inch deficit recorded in a <a href="http://www.sierraphotography.com/wxnotes/RecordSettingEarlySeasonStormLaNinaConsolidatesHowMightASecondYearLaNinaImpact2011USWinterPrecipitation.aspx" target="_blank">selection
of similar second year La Nina years</a>. According to data compiled by the NWS Santa
Barbara will end the water year at about 66% of normal; Camarillo/Oxnard at 57%; Burbank
Airport at 51%; LAX at 59%; and Long Beach Airport at 62%.
</p>
<p>
<span class="dropcap">T</span>his TAO/Triton plot of Pacific equatorial SST and anomaly
clearly depicts the evolution of our two year La Nina and the recent transition to
warmer conditions. Is an El Nino in the works for this Winter? According to the <a href="http://www.esrl.noaa.gov/psd/enso/mei/index.html" target="_blank">Multivariate
ENSO Index</a> (MEI) a transition to El Nino conditions may already be underway. The
April/May value of the MEI was +0.706. This is already within the range of a weak
El Niño ranking. In his June 6 discussion of the MEI climatologist Klaus Wolter noted
the last month's increase in the MEI was the 6th highest increase for this time of
year since 1950. He also pointed out that it was the 4th monthly increase of this
caliber in a row -- second only to the record of six consecutive large monthly increases
in 1997 at the beginning of the mega El Nino of 1997-98. It will be very interesting
to see if the string of large increases in the MEI continues with the May/June value.
</p>
<p>
<span class="dropcap">W</span>hile the ocean seems to be on board with the El Nino
idea, the atmosphere appears to be balking -- at least for the moment. As of June
24, <a href="wxdata1112/psd_gwo_90d_062412b.gif" rel="wximage" target="_blank">the
AAM component of the GWO</a> was down around -2.0, which is nearly as low as it's
been during year two of the 2010-2012 La Nina. A positive value of AAM is generally
associated with El Nino conditions.
</p>
<p>
<span class="dropcap">M</span>ore information about Southern California weather and
climate can be found using our <a href="weatherlinks.htm">WEATHER LINKS</a> page.
</p>
<div class="clearfloat">
</div>
</div>
<img width="0" height="0" src="http://www.sierraphotography.com/wxnotes/aggbug.ashx?id=a3e52768-20db-4c98-a8ea-206305ba9b2b" />
<br />
<hr />Southern California Weather Notes Copyright 2000-2017 Gary Valle. All Rights Reserved.climateEl NinoGlobal Wind Oscillation (GWO)La NinaLos Angeles rainfallMultivariate ENSO Index (MEI)weatherhttp://www.sierraphotography.com/wxnotes/Trackback.aspx?guid=8ee80ce1-c434-431c-af9c-a30eec982360http://www.sierraphotography.com/wxnotes/pingback.aspxhttp://www.sierraphotography.com/wxnotes/PermaLink,guid,8ee80ce1-c434-431c-af9c-a30eec982360.aspxGary Valle

Downtown Los Angeles (USC) recorded 0.49 inch for the
storm, increasing April's rainfall total to 1.71 inches. This is almost double April's
normal of 0.91 inches. The water year total rainfall for Downtown Los Angeles now
stands at 8.68 inches; which is about 60% of normal at this point in the water year.
The water year extends from July 1 to June 30.

Some of the video of yesterday's rainstorm looked more
like coverage of a hurricane rather than an April storm in Los Angeles. There were
flooded streets and creeks, lightning strikes of aircraft and gas lines, strong winds,
waterspouts, hail, toppled trees, mountain snow and more. Downtown Los Angeles (USC)
set a new rainfall record for the date of 0.49 inches, breaking a record set in 1956.

Downtown Los Angeles (USC) recorded 0.95 inch for the
storm, bringing the 2011-2012 water year total to 6.93 inches. This boosts the water
year total to 51% of normal. The wet weather the last two weekends makes March the
wettest month of the rain season to date at Los Angeles. It may have taken the edge
off a very dry rain season for the moment, but rainfall
totals the past 30 days have still been below normal in much of Southern California
and additional rainfall would really help.

The good news is it looks like the current progressive
pattern of West Coast troughs will continue into April. While at the moment it appears
the next trough in the series won't produce more than a smattering of rain south of
Pt. Conception, the ECMWF has been relatively consistent in bringing in a system similar
to our last storm weekend after next. That's a long way out, and the GFS and GEFS
don't agree with the ECMWF, but we'll see!

Update 04/02/12. Saturday's system produced a little more rain than expected
south of Pt. Conception. Downtown Los Angeles (USC) recorded 0.04 inch for the storm,
bringing the 2011-2012 water year total to 6.97 inches. Here are some
rainfall totals from around the area compiled by the NWS. At the moment it looks
like a disturbance rotating around a large Gulf of Alaska low will probably not elongate
and deepen the low enough to produce rain in Southern California, but will result
in cooler temperatures Wednesday and Thursday. Higher pressure is forecast to build
in behind the trough, with a warming trend forecast through Easter weekend.

The IRI/CPC
mid-March plume of forecasts made by dynamical and statistical models for SST
in the Nino 3.4 region suggest ENSO Neutral conditions will persist through boreal
autumn 2012. However, as climatologist
Klaus Wolter points out, all ten of the two-year La Niña events between 1900 and
2009 either continued as a La Niña event for a third year (four of ten), or switched
to El Niño (six of ten), with none of them becoming ENSO-neutral.

More information about Southern California weather and
climate can be found using our WEATHER LINKS page.

Southern California Weather Notes Copyright 2000-2017 Gary Valle. All Rights Reserved.
March Wettest Month This Rain Season, But Still Below Normal. La Nina Done; El Nino on the Horizon?http://www.sierraphotography.com/wxnotes/PermaLink,guid,4cc1aaca-ee43-4d25-9b60-0abf941d400f.aspxhttp://www.sierraphotography.com/wxnotes/MarchWettestMonthThisRainSeasonButStillBelowNormalLaNinaDoneElNinoOnTheHorizon.aspx
Thu, 29 Mar 2012 18:32:16 GMT
<div id="mainwx">
<div class="fltlft">
<p align="center">
<a title="NRL GOES-15 Visible/IR Satellite Image from Sunday, March 25, 2012 at 1:31 pm PDT" href="wxdata1112/20120325.2031.goes_15.visir.bckgr.NE_Pacific_Overview.DAYb.jpg" rel="wximage" target="_blank"> <img border="0" alt="NRL GOES-15 Visible/IR Satellite Image from Sunday, March 25, 2012 at 1:31 pm PDT" src="wxdata1112/20120325.2031.goes_15.visir.bckgr.NE_Pacific_Overview.DAYc.jpg" width="300" height="225" /> </a> <img alt="Click" src="images/click.gif" width="16" height="34" />
<br />
<span class="fontxxsmall">NRL GOES-15 Visible/IR Satellite Image<br />
Sunday, March 25, 2012 at 1:31 pm PDT</span>
</p>
</div>
<p>
<span class="dropcap">L</span>ow pressure "alow and aloft" and associated surface
boundaries resulted in some higher than expected rainfall totals Sunday. Gauges in
the Santa Monica Mountains generally recorded from 2-3 inches of rain, Valleys and
the Metro area 1-2 inches, and Los Angeles County mountains 1-2.5 inches. Here are <a href="wxdata1112/RRMLOX032612_0630PDT.pdf" target="_blank">some
preliminary rainfall totals from around the area</a> compiled by the NWS, and a <a href="wxdata1112/VCWPD_2day_032612_0630d.jpg" target="_blank">snapshot
of a Ventura County Watershed Protection District Google Map</a> with some additional
rainfall totals.
</p>
<p>
<span class="dropcap">D</span>owntown Los Angeles (USC) recorded 0.95 inch for the
storm, bringing the 2011-2012 water year total to 6.93 inches. This boosts the water
year total to 51% of normal. The wet weather the last two weekends makes March the
wettest month of the rain season to date at Los Angeles. It may have taken the edge
off a very dry rain season for the moment, but <a href="wxdata1112/wrcc_pon_30day_032712b.gif" rel="wximage" target="_blank">rainfall
totals the past 30 days</a> have still been below normal in much of Southern California
and additional rainfall would really help.
</p>
<p>
<span class="dropcap">T</span>he good news is it looks like the current progressive
pattern of West Coast troughs will continue into April. While at the moment it appears
the next trough in the series won't produce more than a smattering of rain south of
Pt. Conception, the ECMWF has been relatively consistent in bringing in a system similar
to our last storm weekend after next. That's a long way out, and the GFS and GEFS
don't agree with the ECMWF, but we'll see!
</p>
<p>
<i>Update 04/02/12</i>. Saturday's system produced a little more rain than expected
south of Pt. Conception. Downtown Los Angeles (USC) recorded 0.04 inch for the storm,
bringing the 2011-2012 water year total to 6.97 inches. Here are <a href="wxdata1112/RRMLOX040112_1616PDT.pdf" target="_blank">some
rainfall totals from around the area</a> compiled by the NWS. At the moment it looks
like a disturbance rotating around a large Gulf of Alaska low will probably not elongate
and deepen the low enough to produce rain in Southern California, but will result
in cooler temperatures Wednesday and Thursday. Higher pressure is forecast to build
in behind the trough, with a warming trend forecast through Easter weekend.
</p>
<p>
<span class="dropcap">A</span>ccording to the <a href="http://www.bom.gov.au/climate/enso/archive/ensowrap_20120327.pdf" target="_blank">Australian
Bureau of Meteorology ENSO Wrap-up</a>, issued March 27, the 2011–12 La Niña event
has ended, with key indicators returning to neutral levels.
</p>
<p>
<span class="dropcap">T</span>he <a href="wxdata1112/IRI-CPC_ENSO_PredPlumeMar2012.gif" rel="wximage" target="_blank">IRI/CPC
mid-March plume of forecasts</a> made by dynamical and statistical models for SST
in the Nino 3.4 region suggest ENSO Neutral conditions will persist through boreal
autumn 2012. However, as<a href="http://www.esrl.noaa.gov/psd/enso/mei/index.html" target="_blank"> climatologist
Klaus Wolter</a> points out, all ten of the two-year La Niña events between 1900 and
2009 either continued as a La Niña event for a third year (four of ten), or switched
to El Niño (six of ten), with none of them becoming ENSO-neutral.
</p>
<p>
<span class="dropcap">M</span>ore information about Southern California weather and
climate can be found using our <a href="weatherlinks.htm">WEATHER LINKS</a> page.
</p>
<div class="clearfloat">
</div>
</div>
<img width="0" height="0" src="http://www.sierraphotography.com/wxnotes/aggbug.ashx?id=4cc1aaca-ee43-4d25-9b60-0abf941d400f" />
<br />
<hr />Southern California Weather Notes Copyright 2000-2017 Gary Valle. All Rights Reserved.El NinoLa NinaLos Angeles rainfallprecipitation outlookweatherhttp://www.sierraphotography.com/wxnotes/Trackback.aspx?guid=1d746e22-b4ba-4a13-83b5-43884e87ce8bhttp://www.sierraphotography.com/wxnotes/pingback.aspxhttp://www.sierraphotography.com/wxnotes/PermaLink,guid,1d746e22-b4ba-4a13-83b5-43884e87ce8b.aspxGary Valle

GOES-15 Water Vapor Image
Saturday, March 17, 2012 at 12:00 pm PDT

Updated 03/29/12. Edited to include the rainfall total from October 5 in the
Downtown Los Angeles rainfall comparison.

Although there were scattered
showers throughout much of Southern California Sunday morning, the Los Angeles
Marathon beat the 70/30 odds for measurable rain and stayed dry. Given the cool and
breezy conditions, I'm sure runners were glad the precipitation forecast worked out
on the dry side!

According to KCQT data Downtown Los Angeles (USC)recorded
0.76 inch for the storm, bringing the water year total to 5.98 inches, which is 46%
of normal for the date. This was less than the 1.15 inch recorded Downtown on October
5, the 0.90 inch recorded on November 20, and the 0.96 inch recorded December 12-13,
but in some areas Saturday's storm was wetter than any of these storms.

On a run in the Santa Monica Mountains Sunday morning,
I found melting
graupel in the Santa Monica Mountains at an elevation of about 2300' along Castro
Mtwy about a mile east of Castro Peak. This cell that appears to be the best candidate
for the producing the graupel is shown in this KVTX
NEXRAD radar image from about 9:00 am PDT Saturday morning.

Both the GFS and ECMWF medium range models show a trough
evolving into an upper level low just off the Central California coast this weekend.
It's too early to put much credence in the forecast, but some precipitation in the
Saturday to Monday timeframe looks like a possibility. We'll see!

More information about Southern California weather and
climate can be found using our WEATHER LINKS page.

Southern California Weather Notes Copyright 2000-2017 Gary Valle. All Rights Reserved.
Los Angeles Marathon Cool and Breezy, But Dry. Strong Winds Enhance Foothill and Mountain Precipitation.http://www.sierraphotography.com/wxnotes/PermaLink,guid,1d746e22-b4ba-4a13-83b5-43884e87ce8b.aspxhttp://www.sierraphotography.com/wxnotes/LosAngelesMarathonCoolAndBreezyButDryStrongWindsEnhanceFoothillAndMountainPrecipitation.aspx
Tue, 20 Mar 2012 16:55:59 GMT
<div id="mainwx">
<div class="fltlft">
<p align="center">
<a title="GOES-15 Water Vapor Image from Saturday, March 17, 2012 at 12:00 pm PDT" href="wxdata1112/goes15wv031712_1900zb.gif" rel="wximage" target="_blank"> <img border="0" alt="GOES-15 Water Vapor Image from Saturday, March 17, 2012 at 12:00 pm PDT" src="wxdata1112/goes15wv031712_1900zc.gif" width="300" height="225" /> </a> <img alt="Click" src="images/click.gif" width="16" height="34" />
<br />
<span class="fontxxsmall">GOES-15 Water Vapor Image<br />
Saturday, March 17, 2012 at 12:00 pm PDT</span>
</p>
</div>
<p>
<i>Updated 03/29/12</i>. Edited to include the rainfall total from October 5 in the
Downtown Los Angeles rainfall comparison.
</p>
<p>
<span class="dropcap">A</span>lthough there were <a href="wxdata1112/NEXRAD_region_031812_1757zb.png" rel="wximage" target="_blank">scattered
showers throughout much of Southern California</a> Sunday morning, the Los Angeles
Marathon beat the 70/30 odds for measurable rain and stayed dry. Given the cool and
breezy conditions, I'm sure runners were glad the precipitation forecast worked out
on the dry side!
</p>
<p>
<span class="dropcap">A</span>ccording to KCQT data Downtown Los Angeles (USC)recorded
0.76 inch for the storm, bringing the water year total to 5.98 inches, which is 46%
of normal for the date. This was less than the 1.15 inch recorded Downtown on October
5, the 0.90 inch recorded on November 20, and the 0.96 inch recorded December 12-13,
but in some areas Saturday's storm was wetter than any of these storms.
</p>
<p>
<span class="dropcap">B</span>ecause of the very strong southwesterly inflow that
accompanied the storm, upslope precipitation enhancement produced some impressive
totals in the foothills and mountains. For example, West Fork Heliport recorded 3.82
inches, OPIDS Camp 4.49 inches, Mt. Baldy 3.76 inches, and Nordhoff Ridge 5.32 inches.
Here are <a href="wxdata1112/RRMLOX031912_1653PDT.pdf" target="_blank">some preliminary
rainfall totals from around the area</a> compiled by the NWS, and a <a href="wxdata1112/VCWPD_7day_032012.pdf" target="_blank">snapshot
of a Ventura County Watershed Protection District Google Map</a> (PDF) with some additional
rainfall totals.
</p>
<p>
<span class="dropcap">H</span>ere are a <a href="wxdata1112/NEXRAD_region_031712_1900zb.png" rel="wximage" target="_blank">NEXRAD
regional radar image</a>, <a href="wxdata1112/goes15wv031712_1900zb.gif" rel="wximage" target="_blank">water
vapor satellite image</a>, <a href="wxdata1112/goes15ir031712_1900zb.gif" rel="wximage" target="_blank">IR
satellite image</a> and <a href="wxdata1112/RAMDIS_goes15vis031712_1900zb.jpg" rel="wximage" target="_blank">RAMDIS
visible satellite image</a> of the system at noon Saturday. The parent low north of
Pt. Conception is beautifully structured and there is strong convection associated
with the frontal boundary south of the Los Angeles.
</p>
<p>
<span class="dropcap">O</span>n a run in the Santa Monica Mountains Sunday morning,
I found <a title="Melting graupel in the Santa Monica Mountains along Castro Mtwy 03/18/12." href="wxdata1112/GraupelnrCastroPk1150526d.jpg" rel="wximage" target="_blank">melting
graupel in the Santa Monica Mountains</a> at an elevation of about 2300' along Castro
Mtwy about a mile east of Castro Peak. This cell that appears to be the best candidate
for the producing the graupel is shown in this <a href="wxdata1112/kvtx20120317_155720b.png" rel="wximage" target="_blank">KVTX
NEXRAD radar image</a> from about 9:00 am PDT Saturday morning.
</p>
<p>
<span class="dropcap">B</span>oth the GFS and ECMWF medium range models show a trough
evolving into an upper level low just off the Central California coast this weekend.
It's too early to put much credence in the forecast, but some precipitation in the
Saturday to Monday timeframe looks like a possibility. We'll see!
</p>
<p>
<span class="dropcap">M</span>ore information about Southern California weather and
climate can be found using our <a href="weatherlinks.htm">WEATHER LINKS</a> page.
</p>
<div class="clearfloat">
</div>
</div>
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<br />
<hr />Southern California Weather Notes Copyright 2000-2017 Gary Valle. All Rights Reserved.Los Angeles rainfallprecipitation outlookweatherhttp://www.sierraphotography.com/wxnotes/Trackback.aspx?guid=57bd67ae-9747-4e86-aec0-991032700195http://www.sierraphotography.com/wxnotes/pingback.aspxhttp://www.sierraphotography.com/wxnotes/PermaLink,guid,57bd67ae-9747-4e86-aec0-991032700195.aspxGary Valle

BUFKIT Display of WRF Precipitation Forecast
03/16/12 12z

Updated 03/29/12. Edited to correct the date for the most rainfall in a day
this season (through March 16) at Los Angeles.

It's been a bleak rain season. So far the most rainfall
Los Angeles has recorded in a day this season was in the record-setting
early season storm October 5, when Downtown recorded 1.15 inch of rain. As of
today Los Angeles' water year rainfall total stands at a meager 41% of normal.

If current forecasts verify, the rainfall total at Los
Angeles for this weekend's storm might exceed last October's storm. Maybe. BUFKIT
display of WRF ensemble precipitation forecast shows a spread from 0.4
inch to about 1.1 inch at LAX, and from about 0.65
inch to 1.6 inch at Van Nuys. The 18z WRF/NAM run was wetter than the 12z run
producing about 0.95 inch at LAX and 1.1 inch at Van Nuys. A strong southwesterly
inflow of around 35-40 kts is forecast and could produce higher precipitation amounts
on foothill and mountain slopes which have a southerly to westerly aspect.

The Los Angeles Marathon is this Sunday, and after last
year's record-setting Marathon day rainfall, many are wondering about the weather
on Sunday. Last year of 19,798 runners that completed the race, more than 10,000 were
on the course for longer than 5 hours and nearly 2000 were out there for longer than
7 hours. The Elite Men and most of the runners start at 7:24 am, so the majority of
runners will finish after noon.

Check
with the NWS for the latest official information, but as it looks now the bulk
of the rain is forecast to occur on Saturday and the Marathon will be run after the
cold front has passed through the area. This is a different weather scenario than
last year, but one that can produce cold, showery, blustery conditions with strong
winds out of the northwest. In the unstable conditions that typically follow a cold
front heavy showers, gusty winds and even a thunderstorm are possible. The HPC 6-Hour
Probabilistic Precipitation Guidance for the periods ending
10:00 am Sunday morning and 4:00
pm Sunday afternoon indicate a high probability of at least 0.01 inch of rain
in the Los Angeles area. We'll see!

More information about Southern California weather and
climate can be found using our WEATHER LINKS page.

Southern California Weather Notes Copyright 2000-2017 Gary Valle. All Rights Reserved.
Wettest Storm of Season for Los Angeles? Los Angeles Marathon Forecast to be Showery and Cool.http://www.sierraphotography.com/wxnotes/PermaLink,guid,57bd67ae-9747-4e86-aec0-991032700195.aspxhttp://www.sierraphotography.com/wxnotes/WettestStormOfSeasonForLosAngelesLosAngelesMarathonForecastToBeShoweryAndCool.aspx
Fri, 16 Mar 2012 22:15:36 GMT
<div id="mainwx">
<div class="fltlft">
<p align="center">
<a title="WRF Ensemble Precipitation Forecast from 03/16/12 12z" href="wxdata1112/BUFKIT_eWRF_VNY_031612_12zb.png" rel="wximage" target="_blank"> <img border="0" alt="WRF Ensemble Precipitation Forecast from 03/16/12 12z" src="wxdata1112/BUFKIT_eWRF_VNY_031612_12zc.png" width="300" height="183" /> </a> <img alt="Click" src="images/click.gif" width="16" height="34" />
<br />
<span class="fontxxsmall">BUFKIT Display of WRF Precipitation Forecast<br />
03/16/12 12z</span>
</p>
</div>
<p>
<i>Updated 03/29/12</i>. Edited to correct the date for the most rainfall in a day
this season (through March 16) at Los Angeles.
</p>
<p>
<span class="dropcap">I</span>t's been a bleak rain season. So far the most rainfall
Los Angeles has recorded in a day this season was in the <a href="http://www.sierraphotography.com/wxnotes/WettestStormOfSeasonForLosAngelesLosAngelesMarathonForecastToBeShoweryAndCool.aspx" target="_blank">record-setting
early season storm October 5</a>, when Downtown recorded 1.15 inch of rain. As of
today Los Angeles' water year rainfall total stands at a meager 41% of normal.
</p>
<p>
<span class="dropcap">I</span>f current forecasts verify, the rainfall total at Los
Angeles for this weekend's storm might exceed last October's storm. Maybe. BUFKIT
display of WRF ensemble precipitation forecast shows a spread from <a href="wxdata1112/BUFKIT_eWRF_LAX_031612_12zb.png" rel="wximage" target="_blank">0.4
inch to about 1.1 inch at LAX</a>, and from about <a href="wxdata1112/BUFKIT_eWRF_VNY_031612_12zb.png" rel="wximage" target="_blank">0.65
inch to 1.6 inch at Van Nuys</a>. The 18z WRF/NAM run was wetter than the 12z run
producing about 0.95 inch at LAX and 1.1 inch at Van Nuys. A strong southwesterly
inflow of around 35-40 kts is forecast and could produce higher precipitation amounts
on foothill and mountain slopes which have a southerly to westerly aspect.
</p>
<p>
<span class="dropcap">T</span>he Los Angeles Marathon is this Sunday, and after <a href="http://www.sierraphotography.com/wxnotes/default,month,2011-03.aspx" target="_blank">last
year's record-setting Marathon day rainfall</a>, many are wondering about the weather
on Sunday. Last year of 19,798 runners that completed the race, more than 10,000 were
on the course for longer than 5 hours and nearly 2000 were out there for longer than
7 hours. The Elite Men and most of the runners start at 7:24 am, so the majority of
runners will finish after noon.
</p>
<p>
<a href="http://www.wrh.noaa.gov/lox/" target="_blank"> <span class="dropcap">C</span>heck
with the NWS for the latest official information</a>, but as it looks now the bulk
of the rain is forecast to occur on Saturday and the Marathon will be run after the
cold front has passed through the area. This is a different weather scenario than
last year, but one that can produce cold, showery, blustery conditions with strong
winds out of the northwest. In the unstable conditions that typically follow a cold
front heavy showers, gusty winds and even a thunderstorm are possible. The HPC 6-Hour
Probabilistic Precipitation Guidance for the periods <a href="wxdata1112/p06i_pqpf_ge001_2012031618f048.gif" rel="wximage" target="_blank">ending
10:00 am Sunday morning</a> and <a href="wxdata1112/p06i_pqpf_ge001_2012031618f054.gif" rel="wximage" target="_blank">4:00
pm Sunday afternoon</a> indicate a high probability of at least 0.01 inch of rain
in the Los Angeles area. We'll see!
</p>
<p>
<span class="dropcap">M</span>ore information about Southern California weather and
climate can be found using our <a href="weatherlinks.htm">WEATHER LINKS</a> page.
</p>
<div class="clearfloat">
</div>
</div>
<img width="0" height="0" src="http://www.sierraphotography.com/wxnotes/aggbug.ashx?id=57bd67ae-9747-4e86-aec0-991032700195" />
<br />
<hr />Southern California Weather Notes Copyright 2000-2017 Gary Valle. All Rights Reserved.Los Angeles rainfallprecipitation outlookQPF forecastweatherhttp://www.sierraphotography.com/wxnotes/Trackback.aspx?guid=f27fd81c-285a-4914-9409-d1eb67983fc8http://www.sierraphotography.com/wxnotes/pingback.aspxhttp://www.sierraphotography.com/wxnotes/PermaLink,guid,f27fd81c-285a-4914-9409-d1eb67983fc8.aspxGary Valle

ESRL/PSD Analog 8-14 Day Probabilistic Precipitation Forecast
Probability of more than 25mm precipitation from 03/04/12 to 03/10/12.

Wednesday Downtown Los Angeles' water year rainfall total
fell below 50% of normal for the date. With only 5.22 inches of rain in the bucket
it looks like we're headed toward the driest rain season since the record-setting
dry water year of 2006-2007, when a meager 3.21 inches was recorded. If Los Angeles
ends the rain year (June 30) with less than 7.16 inches of precipitation, the 2011-2012
water year would be one of the ten driest on record.

It's been dry throughout most of Southern California
and much of the state. According to data compiled by the NWS Burbank's water year
total now stands at a paltry 34% of normal; Long Beach 49% of normal; Camarillo 42%
of normal; Santa Barbara 56% of normal; and Paso Robles 49% of normal. Southernmost
California has fared a little better with San Diego at about 79% of normal for the
date. Central California rainfall is also well below average with San Francisco at
35% of the normal, San Jose at 26% and Sacramento at 40%.

I received an email recently from a reader asking if
I thought a March Miracle was likely this year. Keeping in mind the chaotic nature
of weather, and that low probability events do sometimes occur, the short answer is
that I don't think it's likely we'll see higher than normal rainfall this March.

In a post in early October I discussed what the impact
of a second year La Nina might be on 2011-12 Winter precipitation in the continental
U.S. For a selection of seven second year La Ninas the coastal Southern California
climate division recorded about 5 to 6 inches less precipitation than normal for the
period November through March. If we take a look at March rainfall in that same selection
of second year La Ninas, four of the seven recorded less than 0.5 inch rain in March,
and only one was well above average -- 4.83 inches in March 1975.

On the climate side of things the active phase of the
MJO has been stalled
in the Indian Ocean, but the 15-day
ensemble ECMWF and several models forecast increased amplitude and eastward propagation.
As a result of strong negative East Asian and Tropical torque events, relative atmospheric
angular momentum is dropping like a rock, with the GWO
taking a big dive into La Nina territory. Should the MJO continue to propagate
and AAM increase over the next 2 weeks, perhaps we'll see the scenario necessary to
generate an extended Pacific jet strong enough to impact the West Coast.

Monday its looking like we may get a little rain and
possibly some lower elevation snow. Goes soundings and model data indicate the Pacific
system is moisture-starved, but it is quite cold and is forecast to have strong dynamics.
A GOES sounding near the systems core showed a 500mb temp of -30°C. Precipitable water
values in the circulation around the low were around 0.6 inch. With such cold air
aloft, and strong system dynamics, strong convection is a possibility. We'll see!

More information about Southern California weather and
climate can be found using our WEATHER LINKS page.

Southern California Weather Notes Copyright 2000-2017 Gary Valle. All Rights Reserved.
Downtown Los Angeles Rainfall Drops Below 50% of Normal. What are the Chances of a March Miracle?http://www.sierraphotography.com/wxnotes/PermaLink,guid,f27fd81c-285a-4914-9409-d1eb67983fc8.aspxhttp://www.sierraphotography.com/wxnotes/DowntownLosAngelesRainfallDropsBelow50OfNormalWhatAreTheChancesOfAMarchMiracle.aspx
Sun, 26 Feb 2012 23:37:30 GMT
<div id="mainwx">
<div class="fltlft">
<p align="center">
<a title="ESRL/PSD Analog 8-14 Day Probabilistic Precipitation Forecast" href="wxdata1112/PSDAnalog8-14gt25mm022612_00zb.jpg" rel="wximage" target="_blank"> <img border="0" alt="ESRL/PSD Analog 8-14 Day Probabilistic Precipitation Forecast" src="wxdata1112/PSDAnalog8-14gt25mm022612_00zc.jpg" width="300" height="183" /> </a> <img alt="Click" src="images/click.gif" width="16" height="34" />
<br />
<span class="fontxxsmall">ESRL/PSD Analog 8-14 Day Probabilistic Precipitation Forecast<br />
Probability of more than 25mm precipitation from 03/04/12 to 03/10/12.</span>
</p>
</div>
<p>
<span class="dropcap">W</span>ednesday Downtown Los Angeles' water year rainfall total
fell below 50% of normal for the date. With only 5.22 inches of rain in the bucket
it looks like we're headed toward the driest rain season since the record-setting
dry water year of 2006-2007, when a meager 3.21 inches was recorded. If Los Angeles
ends the rain year (June 30) with less than 7.16 inches of precipitation, the 2011-2012
water year would be one of the ten driest on record.
</p>
<p>
<span class="dropcap">I</span>t's been dry throughout most of Southern California
and much of the state. According to data compiled by the NWS Burbank's water year
total now stands at a paltry 34% of normal; Long Beach 49% of normal; Camarillo 42%
of normal; Santa Barbara 56% of normal; and Paso Robles 49% of normal. Southernmost
California has fared a little better with San Diego at about 79% of normal for the
date. Central California rainfall is also well below average with San Francisco at
35% of the normal, San Jose at 26% and Sacramento at 40%.
</p>
<p>
<span class="dropcap">I</span> received an email recently from a reader asking if
I thought a March Miracle was likely this year. Keeping in mind the chaotic nature
of weather, and that low probability events do sometimes occur, the short answer is
that I don't think it's likely we'll see higher than normal rainfall this March.
</p>
<p>
<span class="dropcap">I</span>n a post in early October I discussed what the impact
of a second year La Nina might be on 2011-12 Winter precipitation in the continental
U.S. For a selection of seven second year La Ninas the coastal Southern California
climate division recorded about 5 to 6 inches less precipitation than normal for the
period November through March. If we take a look at March rainfall in that same selection
of second year La Ninas, four of the seven recorded less than 0.5 inch rain in March,
and only one was well above average -- 4.83 inches in March 1975.
</p>
<p>
<span class="dropcap">C</span>urrent outlooks are not favorable for higher than average
March precipitation. The Climate Prediction Centers <a href="wxdata1112/CPC_610prcp022612b.gif" rel="wximage" target="_blank">6-10
Day Precipitation Outlook</a>, <a href="wxdata1112/CPC_814prcp022612b.gif" rel="wximage" target="_blank">8-14
Day Precipitation Outlook</a>, and <a href="wxdata1112/CPC_monthprcp022612b.gif" rel="wximage" target="_blank">One
Month Precipitation Outlook</a> all indicate below normal precipitation in Southern
California. The ESRL/PSD Analog Probabilistic Precipitation Forecast is also dry in
the 6-10 and <a href="wxdata1112/PSDAnalog8-14gt25mm022612_00zb.jpg" rel="wximage" target="_blank">8-14
day outlook period</a>, and the <a href="wxdata1112/PSD_EnsembleSpread022612_00zb.png" rel="wximage" target="_blank">PSD
Ensemble Spread</a> does not look encouraging.
</p>
<p>
<span class="dropcap">O</span>n the climate side of things the active phase of the
MJO has been <a href="wxdata1112/BofM_MJO_40day_022412b.gif" rel="wximage" target="_blank">stalled
in the Indian Ocean</a>, but the <a href="wxdata1112/ECMF_phase_51m_full022312b.gif" rel="wximage">15-day
ensemble ECMWF</a> and several models forecast increased amplitude and eastward propagation.
As a result of strong negative East Asian and Tropical torque events, relative atmospheric
angular momentum is dropping like a rock, with the <a href="wxdata1112/PSD_gwo_40d022412b.gif" rel="wximage" target="_blank">GWO
taking a big dive into La Nina territory</a>. Should the MJO continue to propagate
and AAM increase over the next 2 weeks, perhaps we'll see the scenario necessary to
generate an extended Pacific jet strong enough to impact the West Coast.
</p>
<p>
<span class="dropcap">M</span>onday its looking like we may get a little rain and
possibly some lower elevation snow. Goes soundings and model data indicate the Pacific
system is moisture-starved, but it is quite cold and is forecast to have strong dynamics.
A GOES sounding near the systems core showed a 500mb temp of -30°C. Precipitable water
values in the circulation around the low were around 0.6 inch. With such cold air
aloft, and strong system dynamics, strong convection is a possibility. We'll see!
</p>
<p>
<span class="dropcap">M</span>ore information about Southern California weather and
climate can be found using our <a href="weatherlinks.htm">WEATHER LINKS</a> page.
</p>
<div class="clearfloat">
</div>
</div>
<img width="0" height="0" src="http://www.sierraphotography.com/wxnotes/aggbug.ashx?id=f27fd81c-285a-4914-9409-d1eb67983fc8" />
<br />
<hr />Southern California Weather Notes Copyright 2000-2017 Gary Valle. All Rights Reserved.climateGlobal Wind Oscillation (GWO)La NinaLos Angeles rainfallMadden-Julian Oscillation (MJO)precipitation outlookweatherhttp://www.sierraphotography.com/wxnotes/Trackback.aspx?guid=d67678ea-4aed-430d-823a-f6c5b238319fhttp://www.sierraphotography.com/wxnotes/pingback.aspxhttp://www.sierraphotography.com/wxnotes/PermaLink,guid,d67678ea-4aed-430d-823a-f6c5b238319f.aspxGary Valle

Last Sunday's upper level low resulted in a little rain,
mostly south of the L.A. basin, but Southern California and much of the West has been
dry, dry, dry. How dry? Take a look at this plot
of percent of average precipitation for the past 90 days from the Western Regional
Climate Center.

Downtown Los Angeles (USC) has not recorded measurable
rain for more than a month. The last measurable rain was on December 17 when 0.01
inch recorded. The water year precipitation total for Los Angeles has been stuck on
3.76 inches, which is about 2.5 inches below normal. The Sierra has been especially
dry. The Statewide
Summary of Snow Water Content for January 18 reported the snowpack at 10% of normal.
Remarkably, Mammoth Mountain recorded no natural snow between December 5 and January
19!

The good news is the very stubborn West Coast ridge has
finally relented, opening the door to a more zonal flow and a sequence of shortwave
troughs. The change in pattern is forecast to produce significant rain and snow over
most of the West Coast the next few days. The HPC
5-day Precipitation Forecast indicates up to about 5 inches of precipitation in
some areas of the Sierra and North Coast, and over 9 inches in some areas of the Pacific
Northwest.

The change in pattern isn't forecast to produce much
rain south of Pt. Conception, but at this point just about any amount would be helpful.
BUFKIT analysis of WRF Ensemble forecasts for Van Nuys indicate precipitation amounts ranging
from about 0.1 inch to 0.5 inch, beginning sometime this evening and ending midday
Saturday. The 18z NAM precipitation forecast for Van Nuys projects about 0.25 inch
for the storm. Some mountain areas could see somewhat higher precipitation totals,
particularly those with a west-facing aspect.

Another shortwave is forecast to move through the area
Monday. Model projections differ, but we could get a little rain out of that system
as well. We'll see!

Update January 25, 2012 8:00 am PST. Precipitation
totals across the area from Monday's system generally ranged from about 0.3 inch
to 0.75 inch. Downtown Los Angeles (USC) recorded 0.62 inches for the storm. This
combined with the 0.68 inches from Saturday's system boosted the water year total
for Los Angles to 5.06 inches, which is about 75% of normal for the date. The medium
range models have been all over the place. Yesterday the 12z GFS forecast for Monday
morning depicted an upper low and trough on the West Coast, while the ECMWF indicated
some ridging. Here's a GFS/ECMWF
comparison from San Jose State University Meteorology. Given the recent Sudden
Stratospheric Warming (SSW) and rejuvenation
of the MJO there's plenty of uncertainty in the medium range. The ECMWF seems
to like the idea of a relatively fast-moving trough affecting the West Coast sometime
around February 1. We'll see!

Update January 21, 2012 1:30 pm PST. Perhaps because its jet
stream dynamics were more favorable than expected, this first system was a little
stronger and held together a little better south of Pt. Conception than suggested
by the models. Rainfall
totals tabulated by the NWS generally ranged from about 0.2 to 0.7 inch in the
Los Angeles area, with somewhat higher totals recorded in Ventura County and Santa
Barbara County. Model projections have varied on the strength of the system forecast
to move through the area on Monday. The 12z NAM projected about 0.4 inch for Van Nuys;
the 18z NAM about 0.3 inch, and the 12z GFS about 0.5 inch. The system appears similar
to today's, but it looks like the shortwave
trough and vortex max may track more directly into Southern California.

More information about Southern California weather and
climate can be found using our WEATHER LINKS page.

Southern California Weather Notes Copyright 2000-2017 Gary Valle. All Rights Reserved.
West Coast Ridge Relents, But Not Much Rain Expected South of Pt. Conception.http://www.sierraphotography.com/wxnotes/PermaLink,guid,d67678ea-4aed-430d-823a-f6c5b238319f.aspxhttp://www.sierraphotography.com/wxnotes/WestCoastRidgeRelentsButNotMuchRainExpectedSouthOfPtConception.aspx
Fri, 20 Jan 2012 23:33:43 GMT
<div id="mainwx">
<div class="fltlft">
<p align="center">
<a title="HPC 5-Day Precipitation Forecast Issued Friday Afternoon, January 20, 2012" href="wxdata1112/hpc_5dayQPF012012_2149zb.gif" rel="wximage" target="_blank"> <img border="0" alt="HPC 5-Day Precipitation Forecast Issued Friday Afternoon, January 20, 2012" src="wxdata1112/hpc_5dayQPF012012_2149zc.gif" width="300" height="225" /> </a> <img alt="Click" src="images/click.gif" width="16" height="34" />
<br />
<span class="fontxxsmall">HPC 5-Day Precipitation Forecast<br />
Issued Friday Afternoon, January 20, 2012</span>
</p>
</div>
<p>
<span class="dropcap">L</span>ast Sunday's upper level low resulted in a little rain,
mostly south of the L.A. basin, but Southern California and much of the West has been
dry, dry, dry. How dry? Take a look at this <a href="wxdata1112/WRCC90DayPrecipWest011912b.gif" rel="wximage" target="_blank">plot
of percent of average precipitation</a> for the past 90 days from the Western Regional
Climate Center.
</p>
<p>
<span class="dropcap">D</span>owntown Los Angeles (USC) has not recorded measurable
rain for more than a month. The last measurable rain was on December 17 when 0.01
inch recorded. The water year precipitation total for Los Angeles has been stuck on
3.76 inches, which is about 2.5 inches below normal. The Sierra has been especially
dry. The <a href="http://cdec.water.ca.gov/cgi-progs/reports/DLYSWEQ.20120118" target="_blank">Statewide
Summary of Snow Water Content for January 18</a> reported the snowpack at 10% of normal.
Remarkably, Mammoth Mountain recorded no natural snow between December 5 and January
19!
</p>
<p>
<span class="dropcap">T</span>he good news is the very stubborn West Coast ridge has
finally relented, opening the door to a more zonal flow and a sequence of shortwave
troughs. The change in pattern is forecast to produce significant rain and snow over
most of the West Coast the next few days. The <a href="wxdata1112/hpc_5dayQPF012012_2149zb.gif" rel="wximage">HPC
5-day Precipitation Forecast</a> indicates up to about 5 inches of precipitation in
some areas of the Sierra and North Coast, and over 9 inches in some areas of the Pacific
Northwest.
</p>
<p>
<span class="dropcap">T</span>he change in pattern isn't forecast to produce much
rain south of Pt. Conception, but at this point just about any amount would be helpful.
BUFKIT analysis of WRF Ensemble forecasts for Van Nuys indicate precipitation amounts<a href="wxdata1112/eWRF_BUFKIT_VNY_012012_12zb.png" rel="wximage" target="_blank"> ranging
from about 0.1 inch to 0.5 inch</a>, beginning sometime this evening and ending midday
Saturday. The 18z NAM precipitation forecast for Van Nuys projects about 0.25 inch
for the storm. Some mountain areas could see somewhat higher precipitation totals,
particularly those with a west-facing aspect.
</p>
<p>
<span class="dropcap">A</span>nother shortwave is forecast to move through the area
Monday. Model projections differ, but we could get a little rain out of that system
as well. We'll see!
</p>
<p>
<i>Update January 25, 2012 8:00 am PST</i>. <a href="wxdata1112/RRMLOX012412_1300PST.pdf" target="_blank">Precipitation
totals across the area</a> from Monday's system generally ranged from about 0.3 inch
to 0.75 inch. Downtown Los Angeles (USC) recorded 0.62 inches for the storm. This
combined with the 0.68 inches from Saturday's system boosted the water year total
for Los Angles to 5.06 inches, which is about 75% of normal for the date. The medium
range models have been all over the place. Yesterday the 12z GFS forecast for Monday
morning depicted an upper low and trough on the West Coast, while the ECMWF indicated
some ridging. Here's a <a href="wxdata1112/sjsu_500cf144_012412b.gif" rel="wximage" target="_blank">GFS/ECMWF
comparison</a> from San Jose State University Meteorology. Given the recent <a href="wxdata1112/temp30anim012112.gif" rel="wximage" target="_blank">Sudden
Stratospheric Warming</a> (SSW) and <a href="wxdata1112/BOM_rmm.phase.Last40days012312b.png" rel="wximage" target="_blank">rejuvenation
of the MJO</a> there's plenty of uncertainty in the medium range. The ECMWF seems
to like the idea of a relatively fast-moving trough affecting the West Coast sometime
around February 1. We'll see!
</p>
<p>
<i>Update January 21, 2012 1:30 pm PST</i>. Perhaps because its <a href="wxdata1112/goeswestwv012112_1400zb.jpg" rel="wximage" target="_blank">jet
stream dynamics were more favorable</a> than expected, this first system was a <a href="wxdata1112/wsicompradar_012112_1515zb.gif" rel="wximage" target="_blank">little
stronger and held together a little better</a> south of Pt. Conception than suggested
by the models. <a href="wxdata1112/RRMLOX012112_1007PST.pdf" target="_blank">Rainfall
totals tabulated by the NWS</a> generally ranged from about 0.2 to 0.7 inch in the
Los Angeles area, with somewhat higher totals recorded in Ventura County and Santa
Barbara County. Model projections have varied on the strength of the system forecast
to move through the area on Monday. The 12z NAM projected about 0.4 inch for Van Nuys;
the 18z NAM about 0.3 inch, and the 12z GFS about 0.5 inch. The system appears similar
to today's, but it looks like the <a href="wxdata1112/goeswestwv012112_2200zb.jpg" rel="wximage" target="_blank">shortwave
trough and vortex max</a> may track more directly into Southern California.
</p>
<p>
<span class="dropcap">M</span>ore information about Southern California weather and
climate can be found using our <a href="weatherlinks.htm">WEATHER LINKS</a> page.
</p>
<div class="clearfloat">
</div>
</div>
<img width="0" height="0" src="http://www.sierraphotography.com/wxnotes/aggbug.ashx?id=d67678ea-4aed-430d-823a-f6c5b238319f" />
<br />
<hr />Southern California Weather Notes Copyright 2000-2017 Gary Valle. All Rights Reserved.Los Angeles rainfallMadden-Julian Oscillation (MJO)precipitation outlookQPF forecastSudden Stratospheric Warming (SSW)weatherhttp://www.sierraphotography.com/wxnotes/Trackback.aspx?guid=3bc7e4d1-d958-4a34-8831-150ff4f8521fhttp://www.sierraphotography.com/wxnotes/pingback.aspxhttp://www.sierraphotography.com/wxnotes/PermaLink,guid,3bc7e4d1-d958-4a34-8831-150ff4f8521f.aspxGary Valle

There's been no rainfall recorded at Downtown Los Angeles
(USC) since December 17 when 0.01 inch recorded. Los Angeles ended December with 1.01
inch of rain. This is less than half of normal for the month and far less than last
December's deluge of 10.23 inches.

Even though December 2011 was somewhat dry, it comes
nowhere near setting a record. Since 1877 there have been eight Decembers in which
no rain was recorded, and 44 Decembers with 1.01 inches of rain or less.

Downtown begins 2012 with a water year rainfall total
of 3.76 inches. Last year we would have said this was near normal, but using the new
normals derived from 1981-2010 data the total is 0.56 inch below normal. It has been
several years since Downtown Los Angeles (USC) recorded below normal rainfall for
the first six months of the water year. The last time was July 1 to December 31, 2007.

The MJO has been relatively active this autumn and after
going on a two week holiday appeared to be more
coherent as it moved into the Western Pacific between Christmas and New Year's.
However the NCEP
GEFS and several other models forecast the MJO to rapidly diminish in amplitude
and eastward propagation.

The November 30 - December 1, 2011 downslope windstorm
felled thousands of trees, produced multi-day power outages and resulted in millions
of dollars of damage in valley communities along the San Gabriel Mountains. An initial
analysis of the conditions leading up to the event suggest a combination of factors
contributed to the strength of the winds. Among them were a highly amplified and energetic
north-south upper flow which was evolving into a cutoff upper low over southeastern
California; a deepening surface low south of Las Vegas; cold air advection; and a
possible inversion near mountain-top level.

More information about Southern California weather and
climate can be found using our WEATHER LINKS page.

Southern California Weather Notes Copyright 2000-2017 Gary Valle. All Rights Reserved.
Los Angeles Rainfall Now Falling Behind. Postcard Weather for Rose Parade. MJO Active Again, but for How Long? Millions in Damage from Downslope Windstorm.http://www.sierraphotography.com/wxnotes/PermaLink,guid,3bc7e4d1-d958-4a34-8831-150ff4f8521f.aspxhttp://www.sierraphotography.com/wxnotes/LosAngelesRainfallNowFallingBehindPostcardWeatherForRoseParadeMJOActiveAgainButForHowLongMillionsInDamageFromDownslopeWindstorm.aspx
Mon, 02 Jan 2012 00:05:47 GMT
<div id="mainwx">
<div class="fltlft">
<p align="center">
<a title="CPC 6-10 Day Outlook Precipitation Probability, issued Sunday, January 1, 2012" href="wxdata1112/cpc610prcp010112b.gif" rel="wximage" target="_blank"> <img border="0" alt="CPC 6-10 Day Outlook Precipitation Probability, issued Sunday, January 1, 2012" src="wxdata1112/cpc610prcp010112c.gif" width="300" height="200" /> </a> <img alt="Click" src="images/click.gif" width="16" height="34" />
<br />
<span class="fontxxsmall">CPC 6-10 Day Outlook Precipitation Probability<br />
Issued Sunday, January 1, 2012</span>
</p>
</div>
<p>
<span class="dropcap">T</span>here's been no rainfall recorded at Downtown Los Angeles
(USC) since December 17 when 0.01 inch recorded. Los Angeles ended December with 1.01
inch of rain. This is less than half of normal for the month and far less than last
December's deluge of 10.23 inches.
</p>
<p>
<span class="dropcap">E</span>ven though December 2011 was somewhat dry, it comes
nowhere near setting a record. Since 1877 there have been eight Decembers in which
no rain was recorded, and 44 Decembers with 1.01 inches of rain or less.
</p>
<p>
<span class="dropcap">D</span>owntown begins 2012 with a water year rainfall total
of 3.76 inches. Last year we would have said this was near normal, but using the new
normals derived from 1981-2010 data the total is 0.56 inch below normal. It has been
several years since Downtown Los Angeles (USC) recorded below normal rainfall for
the first six months of the water year. The last time was July 1 to December 31, 2007.
</p>
<p>
<span class="dropcap">I</span>n a word the weather for the Rose Parade is expected
to be SPECTACULAR. The current NWS point forecast for Pasadena is calling for an overnight
low Sunday-Monday of 54 and a high Monday of 83. <a href="http://forecast.weather.gov/MapClick.php?site=lox&amp;textField1=34.1607&amp;textField2=-118.1387&amp;smap=1" target="_blank">Click
here for the latest NWS forecast for Pasadena</a>.
</p>
<p>
<span class="dropcap">T</span>he MJO has been relatively active this autumn and after
going on a two week holiday appeared to be <a href="wxdata1112/MJOLast90days123111b.gif" rel="wximage" target="_blank">more
coherent as it moved into the Western Pacific</a> between Christmas and New Year's.
However the <a href="wxdata1112/NCPE_MJO_123111b.gif" rel="wximage" target="_blank">NCEP
GEFS</a> and several other models forecast the MJO to rapidly diminish in amplitude
and eastward propagation.
</p>
<p>
<span class="dropcap">A</span>t the moment the <a href="wxdata1112/cpc610prcp010112b.gif" rel="wximage" target="_blank">precipitation
outlook</a> continues to be on the dry side. We'll see!
</p>
<p>
<span class="dropcap">T</span>he November 30 - December 1, 2011 downslope windstorm
felled thousands of trees, produced multi-day power outages and resulted in millions
of dollars of damage in valley communities along the San Gabriel Mountains. An initial
analysis of the conditions leading up to the event suggest a combination of factors
contributed to the strength of the winds. Among them were a highly amplified and energetic
north-south upper flow which was evolving into a cutoff upper low over southeastern
California; a deepening surface low south of Las Vegas; cold air advection; and a
possible inversion near mountain-top level.
</p>
<p>
<span class="dropcap">M</span>ore information about Southern California weather and
climate can be found using our <a href="weatherlinks.htm">WEATHER LINKS</a> page.
</p>
<div class="clearfloat">
</div>
</div>
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<br />
<hr />Southern California Weather Notes Copyright 2000-2017 Gary Valle. All Rights Reserved.Los Angeles rainfallLos Angeles temperatureprecipitation outlookweatherhttp://www.sierraphotography.com/wxnotes/Trackback.aspx?guid=83eb7ce0-c90f-4253-8080-48e00398c492http://www.sierraphotography.com/wxnotes/pingback.aspxhttp://www.sierraphotography.com/wxnotes/PermaLink,guid,83eb7ce0-c90f-4253-8080-48e00398c492.aspxGary Valle

GOES-11 Water Vapor Image
Sunday, November 20, 2011 - 11:30 am PST

For the past two years Los Angeles has recorded above
normal rainfall over the first six months of the water year (Jul. 1 to Dec. 31). So
far this year is following suit.

After a record-setting storm in early October in which
Downtown Los Angeles (USC) recorded over an inch or rain, a series of upper level
troughs have continued to bump up the rainfall total. The systems have tended to be
amplifying upper level troughs that split, typically transforming the southern half
of the trough into a difficult-to-forecast cut-off upper level low. The resulting
cut-off lows have then tracked over, along, or off the Southern California coast producing
varying amounts of rain.

Sunday's system was the fourth to produce measurable
rain in Los Angeles this November. A strong
cold front produced very heavy rain, resulting in flooded streets and highways
and resulting in a host of other weather-related problems. In the middle of it all
runners in the PCTR Santa Monica Mountains 9K, 18K, 30K and 50K were running
distances up to 31.5 miles on the trails of Pt. Mugu State Park.

Downtown Los Angeles (USC) recorded 0.90 inches for the
storm, bringing the water year total to 2.75 inches. This is 1.11 inch above the new
1981-2010 normal for rainfall from July 1 through November 22. Here are some additional
(preliminary) precipitation
totals from around the area, compiled by the NWS Los Angeles/Oxnard. More than
an inch above normal sounds like a lot, but as of today only guarantees Los Angeles
precipitation will be above normal through December 12.

Back on July 1 NOAA released
the new 1981-2010 climate normals, replacing the 1971-2000 normals that have been
used this past decade. Normals serve as a 30 year baseline average of climate variables
such as monthly and annual maximum, minimum, and mean temperature; and monthly and
annual total precipitation. For example, Downtown Los Angeles' new normal annual precipitation
total is now 14.93 inches, down from the 15.14 inches we've been using.

After dropping to -0.503 for July/August, and then to
-0.772 for August/September, the September/October value of the Multivariate
ENSO Index (MEI) has dropped a bit more to -.968 sigma. This is well within La
Nina territory, but almost one sigma less than last year's September/October value.
Plots of the Global
Wind Oscillation (GWO) for July
1 to November 19, 2011 and the same
period last year illustrate the year-to-year difference in the atmosphere's response
to La Nina conditions. So far, this year's response is consistent with a more active
MJO and a shift toward a more neutral ENSO state.

While there's still a chance of rain in Southern California
Thanksgiving Day, the forecast is looking better than it did a few days ago when rain
was considered likely. The difficulty in the forecast is yet another upper level trough splitting
into a cut-off upper level low. The 12z NAM forecasts the low to remain
offshore on Thanksgiving Day, and move into Northern Baja by the late afternoon.
The 09z SREF puts the probability of more than 0.01 inch of rain in coastal Southern
California for the 12
hours ending 4:00 pm Thursday at 10% - 30% and the chance
of more than 0.10 inch of rain at around 10%. A shift in the track of the low
toward the coast would significantly increase the chance of rain. We'll see!

More information about Southern California weather and
climate can be found using our WEATHER LINKS page.

Southern California Weather Notes Copyright 2000-2017 Gary Valle. All Rights Reserved.
Los Angeles Starts Water Year Ahead of the Game - Again. Strong Cold Front Hammers Southland. La Nina and the GWO. Thanksgiving Day Rain?http://www.sierraphotography.com/wxnotes/PermaLink,guid,83eb7ce0-c90f-4253-8080-48e00398c492.aspxhttp://www.sierraphotography.com/wxnotes/LosAngelesStartsWaterYearAheadOfTheGameAgainStrongColdFrontHammersSouthlandLaNinaAndTheGWOThanksgivingDayRain.aspx
Wed, 23 Nov 2011 16:47:53 GMT
<div id="mainwx">
<div class="fltlft">
<p align="center">
<a title="GOES-11 Water Vapor Image for Sunday, November 20, 2011 at 11:30 am PST" href="wxdata1112/goes11wv112011_1930zb.gif" rel="wximage" target="_blank"> <img border="0" src="wxdata1112/goes11wv112011_1930zc.gif" width="350" height="263" /> </a> <img alt="Click" src="images/click.gif" width="16" height="34" />
<br />
<span class="fontxxsmall">GOES-11 Water Vapor Image<br />
Sunday, November 20, 2011 - 11:30 am PST</span>
</p>
</div>
<p>
<span class="dropcap">F</span>or the past two years Los Angeles has recorded above
normal rainfall over the first six months of the water year (Jul. 1 to Dec. 31). So
far this year is following suit.
</p>
<p>
<span class="dropcap">A</span>fter a record-setting storm in early October in which
Downtown Los Angeles (USC) recorded over an inch or rain, a series of upper level
troughs have continued to bump up the rainfall total. The systems have tended to be
amplifying upper level troughs that split, typically transforming the southern half
of the trough into a difficult-to-forecast cut-off upper level low. The resulting
cut-off lows have then tracked over, along, or off the Southern California coast producing
varying amounts of rain.
</p>
<p>
<span class="dropcap">S</span>unday's system was the fourth to produce measurable
rain in Los Angeles this November. A <a href="wxdata1112/wsicompradar_112011_1930zb.gif" rel="wximage" target="_blank">strong
cold front produced very heavy rain</a>, resulting in flooded streets and highways
and resulting in a host of other weather-related problems. In the middle of it all
runners in the PCTR Santa Monica Mountains 9K, 18K, 30K and 50K were <a href="http://vimeo.com/32463662" target="_blank">running
distances up to 31.5 miles</a> on the trails of Pt. Mugu State Park.
</p>
<p>
<span class="dropcap">D</span>owntown Los Angeles (USC) recorded 0.90 inches for the
storm, bringing the water year total to 2.75 inches. This is 1.11 inch above the new
1981-2010 normal for rainfall from July 1 through November 22. Here are some additional
(preliminary) <a href="wxdata1112/RRMLOX112011_2200PST.pdf" target="_blank">precipitation
totals</a> from around the area, compiled by the NWS Los Angeles/Oxnard. More than
an inch above normal sounds like a lot, but as of today only guarantees Los Angeles
precipitation will be above normal through December 12.
</p>
<p>
<span class="dropcap">B</span>ack on July 1 NOAA <a href="http://www.noaanews.noaa.gov/stories2011/20110629_newnormals.html" target="_blank">released
the new 1981-2010 climate normals</a>, replacing the 1971-2000 normals that have been
used this past decade. Normals serve as a 30 year baseline average of climate variables
such as monthly and annual maximum, minimum, and mean temperature; and monthly and
annual total precipitation. For example, Downtown Los Angeles' new normal annual precipitation
total is now 14.93 inches, down from the 15.14 inches we've been using.
</p>
<p>
<span class="dropcap">A</span>fter dropping to -0.503 for July/August, and then to
-0.772 for August/September, the September/October value of the <a href="http://www.esrl.noaa.gov/psd/enso/mei/index.html" target="_blank">Multivariate
ENSO Index</a> (MEI) has dropped a bit more to -.968 sigma. This is well within La
Nina territory, but almost one sigma less than last year's September/October value.
Plots of the <a href="http://www.esrl.noaa.gov/psd/map/clim/test_maproom.html" target="_blank">Global
Wind Oscillation</a> (GWO) for <a href="wxdata1112/gwo_080111_111911b.png" rel="wximage" target="_blank">July
1 to November 19, 2011</a> and the <a href="wxdata1112/gwo_080110_111910b.png" rel="wximage" target="_blank">same
period last year</a> illustrate the year-to-year difference in the atmosphere's response
to La Nina conditions. So far, this year's response is consistent with a more active
MJO and a shift toward a more neutral ENSO state.
</p>
<p>
<span class="dropcap">W</span>hile there's still a chance of rain in Southern California
Thanksgiving Day, the forecast is looking better than it did a few days ago when rain
was considered likely. The difficulty in the forecast is yet another upper level trough <a href="wxdata1112/nam_009_500_vort_ht_112311_12zb.gif" rel="wximage" target="_blank">splitting
into a cut-off upper level low</a>. The 12z NAM forecasts the low to <a href="wxdata1112/nam_027_500_vort_ht_112311_12zb.gif" rel="wximage" target="_blank">remain
offshore on Thanksgiving Day</a>, and move into Northern Baja by the late afternoon.
The 09z SREF puts the probability of more than 0.01 inch of rain in coastal Southern
California for the <a href="wxdata1112/SREFpcp12h_pr01_39_112311_09zb.gif" rel="wximage" target="_blank">12
hours ending 4:00 pm Thursday</a> at 10% - 30% and the <a href="wxdata1112/SREFpcp12h_pr1_39_112311_09zb.gif" rel="wximage" target="_blank">chance
of more than 0.10 inch</a> of rain at around 10%. A shift in the track of the low
toward the coast would significantly increase the chance of rain. We'll see!
</p>
<p>
<span class="dropcap">M</span>ore information about Southern California weather and
climate can be found using our <a href="weatherlinks.htm">WEATHER LINKS</a> page.
</p>
<div class="clearfloat">
</div>
</div>
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<br />
<hr />Southern California Weather Notes Copyright 2000-2017 Gary Valle. All Rights Reserved.climateGlobal Wind Oscillation (GWO)La NinaLos Angeles rainfallMadden-Julian Oscillation (MJO)Multivariate ENSO Index (MEI)precipitation outlookweatherhttp://www.sierraphotography.com/wxnotes/Trackback.aspx?guid=bd4674f6-87ba-48db-9248-047e3c22d8aahttp://www.sierraphotography.com/wxnotes/pingback.aspxhttp://www.sierraphotography.com/wxnotes/PermaLink,guid,bd4674f6-87ba-48db-9248-047e3c22d8aa.aspxGary Valle

Enhanced convection in the Western Pacific associated
with active phase of the MJO, and an extension
of the North Pacific Jet caused by a positive
East Asian mountain torque event appeared to have contributed to the unseasonable
amount of rainfall. As observed by Ed Berry (Atmospheric
Insights, Dec. 30, 2007), "...the MJO itself does not generate enough extratropical
westerly wind flow to allow the East Asian jet to impact the USA west coast. A strong
positive East Asian mountain torque needs to be involved, on average."

To get an idea of what the impact of a second year La
Nina might be on 2011-12 Winter precipitation in the continental U.S., the ESRL/PSD
US Climate Division Dataset Mapping Page was used to construct a map
of US composite precipitation anomalies for November to March for year two La
Ninas since 1949. The years included were based primarily on MEI rankings, and include
1950-51, 1955-56, 1962-63, 1971-72, 1974-75, 1999-2000 and 2008-09. The base period
was 1971-2000.

For this selection of years the coastal Southern California
climate division recorded about 5 to 6 inches less precipitation than normal for the
period November through March. The percent of normal water year rainfall recorded
at Downtown Los Angeles (USC) ranged from a low of 47% (1971, 7.17"), to a high of
106% (1955, 16.00"). The average rainfall at Los Angeles for these years was 70.5%
of normal, or 10.7".

More information about Southern California weather and
climate can be found using our WEATHER LINKS page.

Southern California Weather Notes Copyright 2000-2017 Gary Valle. All Rights Reserved.
Record-Setting Early Season Storm. La Nina Consolidates. How Might a Second Year La Nina Impact 2011 U.S. Winter Precipitation?http://www.sierraphotography.com/wxnotes/PermaLink,guid,bd4674f6-87ba-48db-9248-047e3c22d8aa.aspxhttp://www.sierraphotography.com/wxnotes/RecordSettingEarlySeasonStormLaNinaConsolidatesHowMightASecondYearLaNinaImpact2011USWinterPrecipitation.aspx
Sat, 08 Oct 2011 21:05:22 GMT
<div id="mainwx">
<div class="fltlft">
<p align="center">
<a title="GOES-11 Water Vapor Image for Wednesday, October 5, 2011 at 11:30 am PDT" href="wxdata1112/goes11wv100511_1830zb.gif" rel="wximage" target="_blank"> <img border="0" src="wxdata1112/goes11wv100511_1830zc.gif" width="350" height="263" /> </a> <img alt="Click" src="images/click.gif" width="16" height="34" />
<br />
<span class="fontxxsmall">GOES-11 Water Vapor Image<br />
Wednesday, October 5, 2011 - 11:30 am PDT</span>
</p>
</div>
<p>
<span class="dropcap">A</span>n unseasonably deep upper level low, unusually strong
170+ kt Pacific jet, and associated cold front combined to produce record-setting
rainfall in Southern California Wednesday, October 5. Rainfall totals exceeded 1.0
inch in many areas.
</p>
<p>
<span class="dropcap">D</span>owntown Los Angeles (USC) recorded 1.15 inches, setting
a new record for the date, and kick-starting the area's rainy season to 0.78 inch
above normal. <a href="wxdata1112/RERLOX100511_1800PDT.pdf" target="_blank">Rainfall
records for the date</a> were also set for LAX, Long Beach, Camarillo, Santa Barbara
and several other locations. It was the first measurable rainfall at Los Angeles since
June 17. Here are some preliminary precipitation totals from the <a href="wxdata1112/RRMLOX100511_1716PDT.pdf" target="_blank">NWS
Los Angeles/Oxnard,</a><a href="wxdata1112/PNSHNX100511_2251PDT.pdf" target="_blank">NWS
San Joaquin Valley/Hanford </a>and <a href="wxdata1112/RRMSGX100611_0609PDT.pdf" target="_blank">NWS
San Diego</a>.
</p>
<p>
<span class="dropcap">E</span>nhanced convection in the Western Pacific associated
with active phase of the MJO, and an <a href="wxdata1112/11100218_jetstream_norhem.gif" rel="wximage" target="_blank">extension
of the North Pacific Jet</a> caused by a <a href="wxdata1112/gltaum.90day.100511.gif" rel="wximage" target="_blank">positive
East Asian mountain torque</a> event appeared to have contributed to the unseasonable
amount of rainfall. As observed by Ed Berry (<a href="http://weatherclimatelink.blogspot.com/2007/12/getting-what-was-expected.html" target="_blank">Atmospheric
Insights, Dec. 30, 2007</a>), "...the MJO itself does not generate enough extratropical
westerly wind flow to allow the East Asian jet to impact the USA west coast. A strong
positive East Asian mountain torque needs to be involved, on average."
</p>
<p>
<span class="dropcap">T</span>he <a href="wxdata1112/gwo_40d_100511b.gif" rel="wximage" target="_blank">increase
in relative AAM shown by the GWO</a> not withstanding, La Nina conditions appear to
be consolidating in the equatorial Pacific. This <a href="wxdata1112/BofMPacificEqAnomaly100511b.gif" rel="wximage" target="_blank">four
month sequence of Pacific Ocean Equatorial Temperature anomaly cross sections</a> shows
substantial subsurface cooling from July 11 to September 11. The <a href="http://www.esrl.noaa.gov/psd/enso/mei/index.html" target="_blank">Multivariate
ENSO Index</a> (MEI) has dropped from -0.5 for July/August to -0.8 for the August/September
season. This drops the MEI from a rank of 16th last month to 13th this month, just
above the quintile definition of a moderate La Niña ranking. Last year the MEI for
August/September ranked 1st in the record since 1950. This <a href="wxdata1112/time_lon_EQ_hf_sst_sst_mean_anom_200910_201110_2011100716.gif" rel="wximage" target="_blank">TAO
time-longitude plot of SST and SST anomaly</a> shows less cooling than last year on
this date.
</p>
<p>
<span class="dropcap">T</span>o get an idea of what the impact of a second year La
Nina might be on 2011-12 Winter precipitation in the continental U.S., the <a href="http://www.esrl.noaa.gov/psd/data/usclimdivs/" target="_blank">ESRL/PSD
US Climate Division Dataset Mapping Page</a> was used to construct a <a href="wxdata1112/LaNinaYear2CompPrecipAnom7cases092111b.png" rel="wximage" target="_blank">map
of US composite precipitation anomalies</a> for November to March for year two La
Ninas since 1949. The years included were based primarily on MEI rankings, and include
1950-51, 1955-56, 1962-63, 1971-72, 1974-75, 1999-2000 and 2008-09. The base period
was 1971-2000.
</p>
<p>
<span class="dropcap">F</span>or this selection of years the coastal Southern California
climate division recorded about 5 to 6 inches less precipitation than normal for the
period November through March. The percent of normal water year rainfall recorded
at Downtown Los Angeles (USC) ranged from a low of 47% (1971, 7.17"), to a high of
106% (1955, 16.00"). The average rainfall at Los Angeles for these years was 70.5%
of normal, or 10.7".
</p>
<p>
<span class="dropcap">M</span>ore information about Southern California weather and
climate can be found using our <a href="weatherlinks.htm">WEATHER LINKS</a> page.
</p>
<div class="clearfloat">
</div>
</div>
<img width="0" height="0" src="http://www.sierraphotography.com/wxnotes/aggbug.ashx?id=bd4674f6-87ba-48db-9248-047e3c22d8aa" />
<br />
<hr />Southern California Weather Notes Copyright 2000-2017 Gary Valle. All Rights Reserved.climateGlobal Wind Oscillation (GWO)La NinaLos Angeles rainfallMadden-Julian Oscillation (MJO)Multivariate ENSO Index (MEI)weatherhttp://www.sierraphotography.com/wxnotes/Trackback.aspx?guid=12240f3c-f004-4f7a-8f76-b062d2c48564http://www.sierraphotography.com/wxnotes/pingback.aspxhttp://www.sierraphotography.com/wxnotes/PermaLink,guid,12240f3c-f004-4f7a-8f76-b062d2c48564.aspxGary Valle

GOES-11 Water Vapor Image
Saturday September 10, 2011 - 6:30 pm PDT

A dynamic cutoff
upper low centered over Southern California produced numerous thunderstorms in
Southern California and a broad area of the southwestern U.S. Saturday. The thunderstorms
produced thousands of lightning strikes, some heavy downpours, hail and strong winds.

Some of the higher rainfall totals reported by the NWS
include Lake Palmdale at 0.98 inch; Palmdale 0.84 inch and Lockwood Valley 0.58 inch.
Downtown Los Angeles recorded a trace. Here's a NWS
Los Angeles/Oxnard tabulation of some rainfall totals from around the area. Here
also is a NWS San Joaquin
Valley/Hanford tabulation of some rainfall totals in the southern San Joaquin
Valley and Sierra.

In a Southern California Weathernotes post in February
I commented that the tough question regarding La Niña was whether warming would continue
into the NH summer, with neutral ENSO conditions prevailing as we move into autumn;
or if the ENSO cycle would swing back toward a La Nina state. It was noted that since
1949, about half of the first year La
Nina episodes have continued into a second or third year.

Climate scientist and Multivariate
ENSO Index (MEI) codeveloper Klaus Wolter first mentioned the roughly 50/50 chance
that La Nina would return following a summer respite in September 2010. A glance at
a plot
of the extended MEI index, going back to 1871 clearly shows a propensity for a
return of La Nina in the year (or years) following stronger La Nina episodes.

In a September
8, 2011 press release NOAA reported that La Nina is back. More precisely, in their September
8 ENSO Diagnostic Discussion CPC states "La Niña conditions have returned and
are expected to gradually strengthen and continue into the Northern Hemisphere winter
2011-12." The Multivariate
ENSO Index (MEI) has dropped below the weak La Nina threshold, and several oceanic
and atmospheric factors are indicative of a reemerging La Nina. There's still a (historically)
slight chance of a return to ENSO neutral conditions this fall, but it doesn't appear
likely. We'll see!

More information about Southern California weather and
climate can be found using our WEATHER LINKS page.

Southern California Weather Notes Copyright 2000-2017 Gary Valle. All Rights Reserved.
Upper Level Low Generates Downpours, Hail and Thousands of Lightning Strikes. La Nina Conditions Return, But Will La Nina Persist?http://www.sierraphotography.com/wxnotes/PermaLink,guid,12240f3c-f004-4f7a-8f76-b062d2c48564.aspxhttp://www.sierraphotography.com/wxnotes/UpperLevelLowGeneratesDownpoursHailAndThousandsOfLightningStrikesLaNinaConditionsReturnButWillLaNinaPersist.aspx
Mon, 12 Sep 2011 20:39:58 GMT
<div id="mainwx">
<div class="fltlft">
<p align="center">
<a title="GOES-11 Water Vapor Image for Saturday, September 10, 2011 at 6:30 pm PDT" href="wxdata1112/goes11wv091111_0130zb.gif" rel="wximage" target="_blank"> <img border="0" src="wxdata1112/goes11wv091111_0130zc.gif" width="350" height="263" /> </a> <img alt="Click" src="images/click.gif" width="16" height="34" />
<br />
<span class="fontxxsmall">GOES-11 Water Vapor Image<br />
Saturday September 10, 2011 - 6:30 pm PDT</span>
</p>
</div>
<p>
<span class="dropcap">A</span> dynamic <a href="wxdata1112/goes11wv091111_0130zb.gif" rel="wximage" target="_blank">cutoff
upper low centered over Southern California</a> produced numerous thunderstorms in
Southern California and a broad area of the southwestern U.S. Saturday. The thunderstorms
produced thousands of lightning strikes, some heavy downpours, hail and strong winds.
</p>
<p>
<span class="dropcap">A</span>ccording to an <a href="http://yubanet.com/regional/15-536-Lightning-Strikes-Hit-California-on-Sept-10-11.php" target="_blank">article
on Yuba.net</a> over 15,000 lightning strikes were recorded in California over the
24 hour period ending 0600 PDT Sunday. This <a href="wxdata1112/TNF_CalifLightning24hr091111_0600PDTb.jpg" rel="wximage" target="_blank">plot
of lightning detections was produced by Tahoe National Forest</a>. (Typically lightning
detections include both cloud-cloud and cloud-ground strokes.)
</p>
<p>
<span class="dropcap">T</span>hunderstorms were widespread in Southern California
and several strong thunderstorms were reported by the NWS. This <a href="wxdata1112/VTX_compradar_091011_1856zb.png" rel="wximage" target="_blank">NWS
NEXRAD image from about noon on Saturday</a> shows several strong cells including
one area flagged as severe. This <a href="wxdata1112/wsicompradartops_091011_2145zb.gif" rel="wximage" target="_blank">composite
image from WSI/Intellicast.com at 2:45 pm PDT</a> shows estimated cloud tops, cell
movement and hail. Half inch hail was reported in several locations by NWS spotters
and there was one report of 1.25 inch hail near Lake Los Angeles. A wide swath of
enhanced thunderstorm activity developed in the afternoon to the <a href="wxdata1112/wsicompradar_091111_0145zb.gif" rel="wximage" target="_blank">north
and northeast of Los Angeles</a>.
</p>
<p>
<span class="dropcap">S</span>ome of the higher rainfall totals reported by the NWS
include Lake Palmdale at 0.98 inch; Palmdale 0.84 inch and Lockwood Valley 0.58 inch.
Downtown Los Angeles recorded a trace. Here's a <a href="wxdata1112/RRMLOX091011_1719PDT.pdf" target="_blank">NWS
Los Angeles/Oxnard tabulation</a> of some rainfall totals from around the area. Here
also is a <a href="wxdata1112/PNSHNX091111_1139PDT.pdf" target="_blank">NWS San Joaquin
Valley/Hanford tabulation</a> of some rainfall totals in the southern San Joaquin
Valley and Sierra.
</p>
<p>
<span class="dropcap">I</span>n a Southern California Weathernotes post in February
I commented that the tough question regarding La Niña was whether warming would continue
into the NH summer, with neutral ENSO conditions prevailing as we move into autumn;
or if the ENSO cycle would swing back toward a La Nina state. It was noted that since
1949, about half of the first year <a href="HowDoesTheLaNinaOf201011CompareToOtherColdENSOEpisodesSince1949.aspx" target="_blank">La
Nina episodes</a> have continued into a second or third year.
</p>
<p>
<span class="dropcap">C</span>limate scientist and <a href="http://www.esrl.noaa.gov/psd/enso/mei/index.html" target="_blank">Multivariate
ENSO Index</a> (MEI) codeveloper Klaus Wolter first mentioned the roughly 50/50 chance
that La Nina would return following a summer respite in September 2010. A glance at
a <a href="http://www.esrl.noaa.gov/psd/enso/mei.ext/ext.ts.jpg" target="_blank">plot
of the extended MEI index</a>, going back to 1871 clearly shows a propensity for a
return of La Nina in the year (or years) following stronger La Nina episodes.
</p>
<p>
In a <a href="http://www.noaanews.noaa.gov/stories2011/20110908_lanina.html" target="_blank">September
8, 2011 press release</a> NOAA reported that La Nina is back. More precisely, in their <a href="wxdata1112/ensodisc090811.pdf" target="_blank">September
8 ENSO Diagnostic Discussion</a> CPC states "La Niña conditions have returned and
are expected to gradually strengthen and continue into the Northern Hemisphere winter
2011-12." The <a href="http://www.esrl.noaa.gov/psd/enso/mei/index.html" target="_blank">Multivariate
ENSO Index</a> (MEI) has dropped below the weak La Nina threshold, and several oceanic
and atmospheric factors are indicative of a reemerging La Nina. There's still a (historically)
slight chance of a return to ENSO neutral conditions this fall, but it doesn't appear
likely. We'll see!
</p>
<p>
<span class="dropcap">M</span>ore information about Southern California weather and
climate can be found using our <a href="weatherlinks.htm">WEATHER LINKS</a> page.
</p>
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</div>
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<hr />Southern California Weather Notes Copyright 2000-2017 Gary Valle. All Rights Reserved.climateLa NinaLos Angeles rainfallMultivariate ENSO Index (MEI)weatherhttp://www.sierraphotography.com/wxnotes/Trackback.aspx?guid=f6847770-b734-47f2-a8ca-57f701b99d75http://www.sierraphotography.com/wxnotes/pingback.aspxhttp://www.sierraphotography.com/wxnotes/PermaLink,guid,f6847770-b734-47f2-a8ca-57f701b99d75.aspxGary Valle

GOES-11 Water Vapor Image
Tuesday June 28, 2011 - 2:30 pm PDT

Tuesday a front associated with an unseasonably strong
Pacific low pressure system broke rainfall records in much of the northern half of
the state. Precipitation records for the date were broken in numerous locations, including
Monterey, San Jose, Oakland, San Francisco, Napa, Sacramento, Redding, Eureka and
Crescent City. Here are archived copies of record reports from the San
Francisco Bay/Monterey NWS Office and the Sacramento
NWS Office.

The front and trough produced a few clouds and cooled
temperatures in the Los Angeles area, but I didn't see any reports of rain. Downtown
Los Angeles (USC) will end the July 1, 2010 to June 30, 2011 water year with 20.20
inches of rain. This is about 133% of the climate normal of 15.14 inches. According
to NWS data Camarillo/Oxnard recorded 139% of normal rainfall, Long Beach 145%, Santa
Barbara 169% and Palmdale 105%.

Looks like temperatures will be warming up for the July
4th weekend. Temperatures are expected to reach into the 80s at the coast, 90's inland
and 100's in the valleys. Desert areas could reach 110 or higher. Models suggest the
possibility of some monsoon moisture moving into the area Sunday or Monday, along
with a chance of thunderstorms in the mountains and deserts. Check the NWS
Los Angeles/Oxnard Office for the latest forecasts and warnings.

More information about Southern California weather and
climate can be found using our WEATHER LINKS page.

Southern California Weather Notes Copyright 2000-2017 Gary Valle. All Rights Reserved.
Record Rainfall in Northern and Central California. Los Angeles Ends Water Year at 133% of Normal Rainfall. Hot Weather Forecast For July 4th Weekend.http://www.sierraphotography.com/wxnotes/PermaLink,guid,f6847770-b734-47f2-a8ca-57f701b99d75.aspxhttp://www.sierraphotography.com/wxnotes/RecordRainfallInNorthernAndCentralCaliforniaLosAngelesEndsWaterYearAt133OfNormalRainfallHotWeatherForecastForJuly4thWeekend.aspx
Thu, 30 Jun 2011 22:30:58 GMT
<div id="mainwx">
<div class="fltlft">
<p align="center">
<a title="GOES-11 Water Vapor Image for Tuesday June 28, 2011 at 2:30 pm PDT" href="wxdata1011/goes11wv_062811_2130zb.gif" rel="wximage" target="_blank"> <img border="0" src="wxdata1011/goes11wv_062811_2130zc.gif" width="350" height="263" /> </a> <img alt="Click" src="images/click.gif" width="16" height="34" />
<br />
<span class="fontxxsmall">GOES-11 Water Vapor Image<br />
Tuesday June 28, 2011 - 2:30 pm PDT</span>
</p>
</div>
<p>
<span class="dropcap">T</span>uesday a front associated with an unseasonably strong
Pacific low pressure system broke rainfall records in much of the northern half of
the state. Precipitation records for the date were broken in numerous locations, including
Monterey, San Jose, Oakland, San Francisco, Napa, Sacramento, Redding, Eureka and
Crescent City. Here are archived copies of record reports from the <a href="wxdata1011/PNSMTR062811_2000.pdf" target="_blank">San
Francisco Bay/Monterey NWS Office</a> and the <a href="wxdata1011/RERSTO062911_0700.pdf" target="_blank">Sacramento
NWS Office</a>.
</p>
<p>
<span class="dropcap">T</span>he front and trough produced a few clouds and cooled
temperatures in the Los Angeles area, but I didn't see any reports of rain. Downtown
Los Angeles (USC) will end the July 1, 2010 to June 30, 2011 water year with 20.20
inches of rain. This is about 133% of the climate normal of 15.14 inches. According
to NWS data Camarillo/Oxnard recorded 139% of normal rainfall, Long Beach 145%, Santa
Barbara 169% and Palmdale 105%.
</p>
<p>
<span class="dropcap">L</span>ooks like temperatures will be warming up for the July
4th weekend. Temperatures are expected to reach into the 80s at the coast, 90's inland
and 100's in the valleys. Desert areas could reach 110 or higher. Models suggest the
possibility of some monsoon moisture moving into the area Sunday or Monday, along
with a chance of thunderstorms in the mountains and deserts. Check the <a href="http://www.wrh.noaa.gov/lox/" target="_blank">NWS
Los Angeles/Oxnard Office</a> for the latest forecasts and warnings.
</p>
<p>
<span class="dropcap">M</span>ore information about Southern California weather and
climate can be found using our <a href="weatherlinks.htm">WEATHER LINKS</a> page.
</p>
<div class="clearfloat">
</div>
</div>
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<br />
<hr />Southern California Weather Notes Copyright 2000-2017 Gary Valle. All Rights Reserved.Los Angeles rainfallLos Angeles temperaturemonsoonrecord rainfallweatherhttp://www.sierraphotography.com/wxnotes/Trackback.aspx?guid=35a8f23d-8187-4e7f-83d7-9e6b6f350f3ehttp://www.sierraphotography.com/wxnotes/pingback.aspxhttp://www.sierraphotography.com/wxnotes/PermaLink,guid,35a8f23d-8187-4e7f-83d7-9e6b6f350f3e.aspxGary Valle

Aqua-MODIS Composite Satellite Image (NRL)
Saturday, June 4, 2011

An unseasonably strong Pacific low pressure system that
stalled about 200 NM off the Central Californio coast set new rainfall records from
San Francisco to Santa Barbara over the weekend. The N-S oriented front associated
with the system was positioned
over Santa Barbara and San Luis Obispo counties much of the weekend, resulting
in unusually high rainfall totals in some areas. Midday Sunday the upper low began
to move east along 35°N, increasing divergence aloft in areas north of Pt. Conception
and producing additional precipitation Sunday afternoon and evening.

Saturday a new rainfall record for the date was set in
San Francisco; and on Saturday and Sunday new rainfall records were set in Stockton,
Modesto, Paso Robles and Santa Maria. Sunday Santa Barbara Airport recorded 1.24 inches
of rain, breaking the record for the date, and increasing the station's rainfall total
for June to the highest since recordkeeping began in 1941. The dissipating front produced
some scattered showers in the Los Angeles area Sunday.

There were some impressive storm totals. Nordhoff Ridge,
in Ventura County, recorded 1.07 inches of rain; Refugio Pass, in Santa Barbara County,
2.64 inches; and Rocky Butte, in San Luis Obispo County, 3.94 inches. Downtown Los
Angeles (USC) recorded a trace of rain on Sunday, leaving our water year (July 1 to
June 30) rainfall total at 20.19 inches. Here is an archived
copy of a NWS Los Angeles/Oxnard compilation of some rainfall totals from around
the area.

Saturday I did a trail run on the 8000-9000 ft. ridge
between Mt. Pinos and Mt. Abel, north of Los Angeles, and was able to observe first-hand
the very strong southerly flow associated with this system, and the spectacular
wave clouds that resulted.

More information about Southern California weather and
climate can be found using our WEATHER LINKS page.

Southern California Weather Notes Copyright 2000-2017 Gary Valle. All Rights Reserved.
Unseasonably Strong Pacific Low Sets Rainfall Records From San Francisco to Santa Barbara.http://www.sierraphotography.com/wxnotes/PermaLink,guid,35a8f23d-8187-4e7f-83d7-9e6b6f350f3e.aspxhttp://www.sierraphotography.com/wxnotes/UnseasonablyStrongPacificLowSetsRainfallRecordsFromSanFranciscoToSantaBarbara.aspx
Tue, 07 Jun 2011 18:43:44 GMT
<div id="mainwx">
<div class="fltlft">
<p align="center">
<a title="Aqua-MODIS Composite Satellite Image (NRL) from Saturday, June 4, 2011" href="wxdata1011/Aqua-MODIS_comp_060411_2230b.jpg" rel="wximage" target="_blank"> <img border="0" src="wxdata1011/Aqua-MODIS_comp_060411_2230c.jpg" width="350" height="263" /> </a> <img alt="Click" src="images/click.gif" width="16" height="34" />
<br />
<span class="fontxxsmall">Aqua-MODIS Composite Satellite Image (NRL)<br />
Saturday, June 4, 2011</span>
</p>
</div>
<p>
<span class="dropcap">A</span>n unseasonably strong Pacific low pressure system that
stalled about 200 NM off the Central Californio coast set new rainfall records from
San Francisco to Santa Barbara over the weekend. The N-S oriented front associated
with the system was <a title="NRL GOES-11 IR satellite image from June 4, 2011 at 5:00 pm" href="wxdata1011/nrl_goes11ir_060511_0000zb.jpg" rel="wximage" target="_blank">positioned
over Santa Barbara and San Luis Obispo counties</a> much of the weekend, resulting
in unusually high rainfall totals in some areas. Midday Sunday the upper low began
to move east along 35°N, increasing divergence aloft in areas north of Pt. Conception
and producing additional precipitation Sunday afternoon and evening.
</p>
<p>
<span class="dropcap">S</span>aturday a new rainfall record for the date was set in
San Francisco; and on Saturday and Sunday new rainfall records were set in Stockton,
Modesto, Paso Robles and Santa Maria. Sunday Santa Barbara Airport recorded 1.24 inches
of rain, breaking the record for the date, and increasing the station's rainfall total
for June to the highest since recordkeeping began in 1941. The dissipating front produced
some scattered showers in the Los Angeles area Sunday.
</p>
<p>
<span class="dropcap">T</span>here were some impressive storm totals. Nordhoff Ridge,
in Ventura County, recorded 1.07 inches of rain; Refugio Pass, in Santa Barbara County,
2.64 inches; and Rocky Butte, in San Luis Obispo County, 3.94 inches. Downtown Los
Angeles (USC) recorded a trace of rain on Sunday, leaving our water year (July 1 to
June 30) rainfall total at 20.19 inches. Here is an <a href="wxdata1011/RRMLOX060611_1114PDT.pdf" target="_blank">archived
copy of a NWS Los Angeles/Oxnard compilation</a> of some rainfall totals from around
the area.
</p>
<p>
<span class="dropcap">S</span>aturday I did a trail run on the 8000-9000 ft. ridge
between Mt. Pinos and Mt. Abel, north of Los Angeles, and was able to observe first-hand
the very strong southerly flow associated with this system, and the <a href="http://www.photographyontherun.com/AtmosphericDynamics.aspx" target="_blank">spectacular
wave clouds that resulted</a>.
</p>
<p>
<span class="dropcap">M</span>ore information about Southern California weather and
climate can be found using our <a href="weatherlinks.htm">WEATHER LINKS</a> page.
</p>
<div class="clearfloat">
</div>
</div>
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<br />
<hr />Southern California Weather Notes Copyright 2000-2017 Gary Valle. All Rights Reserved.Los Angeles rainfallrecord rainfallweatherhttp://www.sierraphotography.com/wxnotes/Trackback.aspx?guid=0241735f-a53c-40fc-96d3-0d5d2d8a714dhttp://www.sierraphotography.com/wxnotes/pingback.aspxhttp://www.sierraphotography.com/wxnotes/PermaLink,guid,0241735f-a53c-40fc-96d3-0d5d2d8a714d.aspxGary Valle

Overall it's been a wet water year in Southern California,
but in the fashion of a Mediterranean climate the wet water year has been comprised
of a patchwork of wet and dry months.

If it were not for an unusually stormy December in which
Downtown Los Angeles recorded 8.32 inches more rain than normal, Los Angeles would
be looking at about 76% of normal rainfall this water year instead of 131%. This reduced
amount would be more typical of the rainfall recorded in Los Angeles during a La Nina
influenced water year.

March was wet, but April and May have been dry. Sunday
morning's wet weather added 0.07 inch to May's total for Los Angeles, but the combined
April/May rainfall deficit is still about 0.9 inch.

It won't take a lot of rain to break the record for May
17 at Downtown Los Angeles -- 0.18 inch would do it -- and it would also raise the
water year rainfall total for Los Angeles to over 20 inches. The previous precipitation
record for May 17 was 0.17", set in 1883. Note: Record for USC Campus (KCQT) is 0.06,
set in 1949, but data from Civic Center is used for Downtown Los Angeles records prior
to 1921.

There's a chance of more rain Wednesday, and then perhaps
again Sunday into Monday. We'll see!

Update Tuesday, May 17, 2011. Rainfall amounts from the storm that affected
Los Angeles last night and this morning were generally within the range projected
by the WRF ensembles. Downtown Los Angeles (USC) recorded 0.15 inch for the storm,
bring the water year total to 19.99 inches. Here's a report
compiled by the NWS with some rainfall totals from around the area. Tonight's
system is forecast to produce similar rainfall totals. At the moment some drizzle
or light rain looks like a possibility in the Los Angeles area Sunday and early Monday.

Update Wednesday, May 18, 2011. Thanks to the system that moved into the area
last night, Downtown Los Angeles (USC) recorded additional rainfall Tuesday evening,
nudging the rainfall total for May 17 up to 0.18 inch, and breaking the old rainfall
record for the date set in 1883. Shower activity appears to be winding down and partly
cloudy skies are forecast for Los Angeles this afternoon. Rainfall totals from the
second system were generally similar to Tuesday's amounts. Here's a report
compiled by the NWS Los Angeles/Oxnard that lists the cumulative rainfall that
has resulted from these two storms for a number of stations around the area. The water
year total for Downtown Los Angeles (USC) now stands at 20.19 inches.

More information about Southern California weather and
climate can be found using our WEATHER LINKS page.

Southern California Weather Notes Copyright 2000-2017 Gary Valle. All Rights Reserved.
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Tue, 17 May 2011 02:32:59 GMT
<div id="mainwx">
<div class="fltlft">
<p align="center">
<a title="BUFKIT Display of Precipitation and Temperature Forecast for VNY from WRF Ensembles 05/16/11 12z" href="wxdata1011/eWRFprecipVNY_051611_12zb.png" rel="wximage" target="_blank"> <img border="0" src="wxdata1011/eWRFprecipVNY_051611_12zc.png" width="350" height="214" /> </a> <img alt="Click" src="images/click.gif" width="16" height="34" />
<br />
<span class="fontxxsmall">BUFKIT - Precipitation and Temperature Forecast<br />
WRF Ensemble for VNY 05/16/11 12z</span>
</p>
</div>
<p>
<span class="dropcap">O</span>verall it's been a wet water year in Southern California,
but in the fashion of a Mediterranean climate the wet water year has been comprised
of a patchwork of wet and dry months.
</p>
<p>
<span class="dropcap">I</span>f it were not for an unusually stormy December in which
Downtown Los Angeles recorded 8.32 inches more rain than normal, Los Angeles would
be looking at about 76% of normal rainfall this water year instead of 131%. This reduced
amount would be more typical of the rainfall recorded in Los Angeles during a La Nina
influenced water year.
</p>
<p>
<span class="dropcap">M</span>arch was wet, but April and May have been dry. Sunday
morning's wet weather added 0.07 inch to May's total for Los Angeles, but the combined
April/May rainfall deficit is still about 0.9 inch.
</p>
<p>
<span class="dropcap">B</span>UFKIT analysis of WRF ensemble data for Van Nuys and
LAX suggests tomorrow's storm is likely to produce between 0.1 inch and 0.3 inch of
rain in the Los Angeles basin, and perhaps up to 0.4 inch in the San Fernando Valley. <a href="wxdata1011/sref_apcp24h_pr0.25_39h_051611_12zb.gif" rel="wximage" target="_blank">SREF
Ensemble probabilities</a> and <a href="wxdata1011/hpc_p06i_pqpf_ge025_2011051618f018.gif" rel="wximage" target="_blank">HPC
Probabilistic Precipitation Guidance</a> support this estimate.
</p>
<p>
<span class="dropcap">I</span>t won't take a lot of rain to break the record for May
17 at Downtown Los Angeles -- 0.18 inch would do it -- and it would also raise the
water year rainfall total for Los Angeles to over 20 inches. The previous precipitation
record for May 17 was 0.17", set in 1883. Note: Record for USC Campus (KCQT) is 0.06,
set in 1949, but data from Civic Center is used for Downtown Los Angeles records prior
to 1921.
</p>
<p>
<span class="dropcap">T</span>here's a chance of more rain Wednesday, and then perhaps
again Sunday into Monday. We'll see!
</p>
<p>
<i>Update Tuesday, May 17, 2011</i>. Rainfall amounts from the storm that affected
Los Angeles last night and this morning were generally within the range projected
by the WRF ensembles. Downtown Los Angeles (USC) recorded 0.15 inch for the storm,
bring the water year total to 19.99 inches. Here's a <a href="wxdata1011/RRMLOX051711_1117PDT.pdf" target="_blank">report
compiled by the NWS</a> with some rainfall totals from around the area. Tonight's
system is forecast to produce similar rainfall totals. At the moment some drizzle
or light rain looks like a possibility in the Los Angeles area Sunday and early Monday.
</p>
<p>
<i>Update Wednesday, May 18, 2011</i>. Thanks to the system that moved into the area
last night, Downtown Los Angeles (USC) recorded additional rainfall Tuesday evening,
nudging the rainfall total for May 17 up to 0.18 inch, and breaking the old rainfall
record for the date set in 1883. Shower activity appears to be winding down and partly
cloudy skies are forecast for Los Angeles this afternoon. Rainfall totals from the
second system were generally similar to Tuesday's amounts. Here's a <a href="wxdata1011/RRMLOX051811_1729PDT.pdf" target="_blank">report
compiled by the NWS Los Angeles/Oxnard</a> that lists the cumulative rainfall that
has resulted from these two storms for a number of stations around the area. The water
year total for Downtown Los Angeles (USC) now stands at 20.19 inches.
</p>
<p>
<span class="dropcap">M</span>ore information about Southern California weather and
climate can be found using our <a href="weatherlinks.htm">WEATHER LINKS</a> page.
</p>
<div class="clearfloat">
</div>
</div>
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<br />
<hr />Southern California Weather Notes Copyright 2000-2017 Gary Valle. All Rights Reserved.La NinaLos Angeles rainfallprecipitation outlookrecord rainfallweatherhttp://www.sierraphotography.com/wxnotes/Trackback.aspx?guid=d9a67f00-6e0d-44b6-981c-6cfb46e77a8ahttp://www.sierraphotography.com/wxnotes/pingback.aspxhttp://www.sierraphotography.com/wxnotes/PermaLink,guid,d9a67f00-6e0d-44b6-981c-6cfb46e77a8a.aspxGary Valle

Running in the rain and wind, and splashing through innumerable
puddles, Markos Geneti set a new Los Angeles Marathon record in a time of 2:06:35.
It was a remarkable performance, in adverse conditions. From 8:00 a.m. to 12:00 p.m.
the Mt. Washington RAWS, near the start of the marathon, recorded 0.59 inches of rain;
and the Beverly Hills RAWS near mile 17, recorded 1.27 inches. Periods of heavy rain
were reported at Santa Monica Airport, near the finish line, through much of the race.
According to a report in the Los Angeles Times sports blog, The Fabulous Forum, thousands
of runners were evaluated for hypothermia and 25 runners were hospitalized.

Many rainfall records were set around the area Sunday,
with some locations recording as much as one-third of a year's normal rainfall in
24 hours! In the early evening rainfall rates of over an inch an hour were recorded
in Woodland Hills and Canoga Park. According to a NWS Storm Report, at 6:14 p.m. a
flash flood was reported in Woodland Hills with "mud and debris flowing down the street"
and "at least four to five vehicles stuck in flowing water."

Downtown Los Angeles (USC) recorded 2.42 inches of rain
yesterday, breaking a record set in 1943. Santa Barbara Airport had its wettest day
on record, recording 5.23 inches of rain. Here's an archived copy of the NWS
Record Report for March 20, listing some of the rainfall records for the day.

Storm totals in excess of 3 inches have been common in
Los Angeles, Ventura, Santa Barbara, and San Luis Obispo counties. Higher totals were
recorded in many areas. As of 5:00 p.m. the NWS reported that Van Nuys had recorded
6.74 inches of rainfall, Northridge 6.08 inches, Newhall 7.20 inches, Santa Barbara
Airport 6.27 inches, San Marcos Pass 10.72 inches, and Gibraltar Dam 11.73 inches.
Here's an archived copy of a NWS
report with some rainfall and snowfall amounts from around the area.

Downtown Los Angeles made up its rainfall deficit for
the month of March and more, increasing its water year rainfall total to 18.55 inches,
or about 123% of normal. This makes the 2010-2011 water year the wettest in Los Angeles
during a La Nina over the last 60 years, surpassing the totals recorded during the
strong La Ninas of 1955-56 (99% of normal) and 1973-74 (106% of normal), and weak
La Ninas of 1967-68 (110%) and 2000-01 (118%).

Sunday's heavy rain appears to have had the earmarks
of an atmospheric river event. NRL
SSM/I IPW imagery (lower right) shows a pre-frontal band of IPW values of 35-40
kg/m2 impinging the coast, NEDIS
blended TPW imagery showed a band of ~25 mm TPW extending some 4000 km to the
longitude of Hawaii. A BUFKIT
cross section based on 12z NAM data for VNY depicted a low level jet (LLJ) structure
coinciding with the period of heaviest rainfall. Research by Dr. F. Martin Ralph,
et. al., observed that in atmospheric rivers over the eastern Pacific, 75% of the
water vapor transport below 500 mb takes place within the lowest 2.25 km and occurs
with LLJ wind structure. In addition in cases where a LLJ is present, there was 50%
greater precipitation efficiency.

More information about Southern California weather and
climate can be found using our WEATHER LINKS page.

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New Record Set at Los Angeles Marathon. New Rainfall Records Set in Los Angeles. Was it an Atmospheric River Event?http://www.sierraphotography.com/wxnotes/PermaLink,guid,d9a67f00-6e0d-44b6-981c-6cfb46e77a8a.aspxhttp://www.sierraphotography.com/wxnotes/NewRecordSetAtLosAngelesMarathonNewRainfallRecordsSetInLosAngelesWasItAnAtmosphericRiverEvent.aspx
Tue, 22 Mar 2011 00:09:13 GMT
<div id="mainwx">
<div class="fltlft">
<p align="center">
<a title="GOES-11 Water Vapor Satellite Image on Sunday, March 20, 2011 at 1:30 p.m." href="wxdata1011/goes11wv_032011_2030zb.gif" rel="wximage" target="_blank"> <img border="0" src="wxdata1011/goes11wv_032011_2030zc.gif" width="350" height="263" /> </a> <img alt="Click" src="images/click.gif" width="16" height="34" />
<br />
<span class="fontxxsmall">GOES-11 Water Vapor Satellite Image<br />
Sunday, March 20, 2011 at 1:30 p.m.</span>
</p>
</div>
<p>
<span class="dropcap">R</span>unning in the rain and wind, and splashing through innumerable
puddles, Markos Geneti set a new Los Angeles Marathon record in a time of 2:06:35.
It was a remarkable performance, in adverse conditions. From 8:00 a.m. to 12:00 p.m.
the Mt. Washington RAWS, near the start of the marathon, recorded 0.59 inches of rain;
and the Beverly Hills RAWS near mile 17, recorded 1.27 inches. Periods of heavy rain
were reported at Santa Monica Airport, near the finish line, through much of the race.
According to a report in the Los Angeles Times sports blog, The Fabulous Forum, thousands
of runners were evaluated for hypothermia and 25 runners were hospitalized.
</p>
<p>
<span class="dropcap">M</span>any rainfall records were set around the area Sunday,
with some locations recording as much as one-third of a year's normal rainfall in
24 hours! In the early evening rainfall rates of over an inch an hour were recorded
in Woodland Hills and Canoga Park. According to a NWS Storm Report, at 6:14 p.m. a
flash flood was reported in Woodland Hills with "mud and debris flowing down the street"
and "at least four to five vehicles stuck in flowing water."
</p>
<p>
<span class="dropcap">D</span>owntown Los Angeles (USC) recorded 2.42 inches of rain
yesterday, breaking a record set in 1943. Santa Barbara Airport had its wettest day
on record, recording 5.23 inches of rain. Here's an archived copy of the <a href="wxdata1011/RERLOX032111_0400PDT.pdf" target="_blank">NWS
Record Report for March 20</a>, listing some of the rainfall records for the day.
</p>
<p>
<span class="dropcap">S</span>torm totals in excess of 3 inches have been common in
Los Angeles, Ventura, Santa Barbara, and San Luis Obispo counties. Higher totals were
recorded in many areas. As of 5:00 p.m. the NWS reported that Van Nuys had recorded
6.74 inches of rainfall, Northridge 6.08 inches, Newhall 7.20 inches, Santa Barbara
Airport 6.27 inches, San Marcos Pass 10.72 inches, and Gibraltar Dam 11.73 inches.
Here's an archived copy of a <a href="wxdata1011/RRMLOX032111_1723PDT.pdf" target="_blank">NWS
report with some rainfall and snowfall amounts</a> from around the area.
</p>
<p>
<span class="dropcap">D</span>owntown Los Angeles made up its rainfall deficit for
the month of March and more, increasing its water year rainfall total to 18.55 inches,
or about 123% of normal. This makes the 2010-2011 water year the wettest in Los Angeles
during a La Nina over the last 60 years, surpassing the totals recorded during the
strong La Ninas of 1955-56 (99% of normal) and 1973-74 (106% of normal), and weak
La Ninas of 1967-68 (110%) and 2000-01 (118%).
</p>
<p>
<span class="dropcap">S</span>unday's heavy rain appears to have had the earmarks
of an atmospheric river event. <a href="wxdata1011/20110320.1305.f-15.multisensor2.jpg" rel="wximage" target="_blank">NRL
SSM/I IPW imagery</a> (lower right) shows a pre-frontal band of IPW values of 35-40
kg/m2 impinging the coast, <a href="wxdata1011/EAST_PACIFIC_TPW_20110321_00Z.png" rel="wximage" target="_blank">NEDIS
blended TPW imagery</a> showed a band of ~25 mm TPW extending some 4000 km to the
longitude of Hawaii. A <a href="wxdata1011/KVNY_NAM_wind_032011_12zb.png" rel="wximage" target="_blank">BUFKIT
cross section</a> based on 12z NAM data for VNY depicted a low level jet (LLJ) structure
coinciding with the period of heaviest rainfall. Research by Dr. F. Martin Ralph,
et. al., observed that in atmospheric rivers over the eastern Pacific, 75% of the
water vapor transport below 500 mb takes place within the lowest 2.25 km and occurs
with LLJ wind structure. In addition in cases where a LLJ is present, there was 50%
greater precipitation efficiency.
</p>
<p>
<span class="dropcap">M</span>ore information about Southern California weather and
climate can be found using our <a href="weatherlinks.htm">WEATHER LINKS</a> page.
</p>
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</div>
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<br />
<hr />Southern California Weather Notes Copyright 2000-2017 Gary Valle. All Rights Reserved.La NinaLos Angeles rainfallrecord rainfallweatherhttp://www.sierraphotography.com/wxnotes/Trackback.aspx?guid=4f8905cd-262a-465e-abec-54087987a3dehttp://www.sierraphotography.com/wxnotes/pingback.aspxhttp://www.sierraphotography.com/wxnotes/PermaLink,guid,4f8905cd-262a-465e-abec-54087987a3de.aspxGary Valle

HPC 3-Day Precipitation Forecast
For the Period Ending 11:00 a.m. Monday, March 21

Along with January and February, March is one of the
big three precipitation months in Southern California in which the average rainfall
for Downtown Los Angeles exceeds 3.0 inches. In January we were about 2.5 inches below
normal rainfall, and in February about 0.4 inch below normal. So far this March, we're
nearly two inches below normal for the month. If it were not for an unusually wet
December in which Los Angeles recorded 8.32 inches above normal rainfall, we'd be
looking at 50% water year right now instead of over 100%.

If today's 12z NAM and GFS forecasts verify, we could
make up that March deficit, and push our water year total up to nearly 120%! According
to these numerical forecasts, we could see two to three inches of rain in the Los
Angeles area by Monday afternoon, and significantly more in orographically favored
foothill and mountain locations. The NAM forecasts moist southerly winds approaching
60 kts at the 5000 ft. level Sunday evening.

BUFKIT analysis of 12z NAM/GFS data generates 2.16/4.11
inches of rain for LAX, 3.56/3.57 inches for Van Nuys, and 4.01/4.20 inches for Santa
Barbara. The GFS brings in the second front faster than the NAM, forecasting the onset
of heavier rain during the day Sunday, rather than Sunday evening. The 09z SREF puts
the probability of more than 1.0 inch of rain in the Los Angeles area for the 24
hour period ending Monday morning at about 90%.

And yes, it does look like there's a chance of rain for
the Los Angeles Marathon. Although the heavies rain is forecast to hold off until
Sunday afternoon or evening, the 09z SREF pegs the probability of 0.1 inch of rain
or more in the Los Angeles area over
the 6 hours ending at 11:00 a.m. Sunday at about 70%. BUFKIT
analysis of 12z NAM data generates about 0.20 inch at LAX from 8:00 a.m. to noon,
with temps in the mid 50's. The GFS says about 0.50 inch over the same period. We'll
see!

Southern California Weather Notes Copyright 2000-2017 Gary Valle. All Rights Reserved.
Rain a Possibility for Los Angeles Marathon. Heavier Rain Expected Sunday Evening; Maybe Earlier.http://www.sierraphotography.com/wxnotes/PermaLink,guid,4f8905cd-262a-465e-abec-54087987a3de.aspxhttp://www.sierraphotography.com/wxnotes/RainAPossibilityForLosAngelesMarathonHeavierRainExpectedSundayEveningMaybeEarlier.aspx
Fri, 18 Mar 2011 19:41:41 GMT
<div id="mainwx">
<div class="fltlft">
<p align="center">
<a title="HPC 3-Day Precipitation Forecast for the Period Ending 11:00 a.m. Monday, March 21." href="wxdata1011/hpc_3dayqpf_031811_1756b.png" rel="wximage" target="_blank"> <img border="0" src="wxdata1011/hpc_3dayqpf_031811_1756c.png" width="350" height="262" /> </a> <img alt="Click" src="images/click.gif" width="16" height="34" />
<br />
<span class="fontxxsmall">HPC 3-Day Precipitation Forecast<br />
For the Period Ending 11:00 a.m. Monday, March 21</span>
</p>
</div>
<p>
<span class="dropcap">A</span>long with January and February, March is one of the
big three precipitation months in Southern California in which the average rainfall
for Downtown Los Angeles exceeds 3.0 inches. In January we were about 2.5 inches below
normal rainfall, and in February about 0.4 inch below normal. So far this March, we're
nearly two inches below normal for the month. If it were not for an unusually wet
December in which Los Angeles recorded 8.32 inches above normal rainfall, we'd be
looking at 50% water year right now instead of over 100%.
</p>
<p>
<span class="dropcap">I</span>f today's 12z NAM and GFS forecasts verify, we could
make up that March deficit, and push our water year total up to nearly 120%! According
to these numerical forecasts, we could see two to three inches of rain in the Los
Angeles area by Monday afternoon, and significantly more in orographically favored
foothill and mountain locations. The NAM forecasts moist southerly winds approaching
60 kts at the 5000 ft. level Sunday evening.
</p>
<p>
<span class="dropcap">B</span>UFKIT analysis of 12z NAM/GFS data generates 2.16/4.11
inches of rain for LAX, 3.56/3.57 inches for Van Nuys, and 4.01/4.20 inches for Santa
Barbara. The GFS brings in the second front faster than the NAM, forecasting the onset
of heavier rain during the day Sunday, rather than Sunday evening. The 09z SREF puts
the probability of more than 1.0 inch of rain in the Los Angeles area for the <a href="wxdata1011/sref_apcp24h_pr1.0_78_031811_09zb.gif" rel="wximage" target="_blank">24
hour period ending Monday morning</a> at about 90%.
</p>
<p>
<span class="dropcap">A</span>nd yes, it does look like there's a chance of rain for
the Los Angeles Marathon. Although the heavies rain is forecast to hold off until
Sunday afternoon or evening, the 09z SREF pegs the probability of 0.1 inch of rain
or more in the Los Angeles area <a href="wxdata1011/sref_apcp6h_pr0.1_57_031811_09zb.gif" rel="wximage" target="_blank">over
the 6 hours ending at 11:00 a.m. Sunday</a> at about 70%. <a title="BUFKIT display of clouds, precipitation (green bars), temperature (red), and wind chill (blue) from 12z NAM 03/18/11 for LAX." href="wxdata1011/bufkit_lax_nam_031811_12zb.png" rel="wximage" target="_blank">BUFKIT
analysis of 12z NAM data</a> generates about 0.20 inch at LAX from 8:00 a.m. to noon,
with temps in the mid 50's. The GFS says about 0.50 inch over the same period. We'll
see!
</p>
<p>
<span class="dropcap">B</span>e sure to check the <a href="http://www.wrh.noaa.gov/lox/" target="_blank">NWS
Los Angeles/Oxnard web site</a> for the latest forecasts, advisories and warnings.
More information about Southern California weather and climate can be found using
our <a href="weatherlinks.htm">WEATHER LINKS</a> page.
</p>
<div class="clearfloat">
</div>
</div>
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<br />
<hr />Southern California Weather Notes Copyright 2000-2017 Gary Valle. All Rights Reserved.Los Angeles rainfallLos Angeles temperatureprecipitation outlookQPF forecastweatherhttp://www.sierraphotography.com/wxnotes/Trackback.aspx?guid=8a13a4c8-1de9-40d5-a4bb-fccd308dd907http://www.sierraphotography.com/wxnotes/pingback.aspxhttp://www.sierraphotography.com/wxnotes/PermaLink,guid,8a13a4c8-1de9-40d5-a4bb-fccd308dd907.aspxGary Valle

The wetter ensemble member forecasts prevailed in last
Friday's and Saturday's rain and snow event. Downtown Los Angeles recorded 1.20 inches
for the storm. This brought the water year total to 15.78 inches, which is about 104%
of normal. Although this might seem unusual in a La Nina influenced rain season, during two
of the strongest La Ninas in the past 60 years -- 1955-56 and 1973-74 -- Los Angeles
recorded 99% and 106% of normal rainfall. Here's an archived copy of a NWS
tabulation of some rainfall totals from around the area from early Friday, February
25, to 10:00 p.m. Saturday, February 26.

The NAM and GFS, as well as the SREF and eWRF ensembles,
had a tough time forecasting the rainfall produced by our current scenario -- a relatively
shallow, moist westerly flow accompanied by modest
jet stream dynamics. As this BUFKIT
time-height cross section shows, the wettest eWRF ensemble member depicted a 125
kt jet max overhead, suggesting the models had some difficulty in forecasting the
structure and strength of the jet. At best, the models forecast a few hundredths of
an inch of rain in the Los Angeles area, but the most recent NWS
tabulation of rainfall totals for the event lists many stations with between 0.1
and 0.25 inch. As of 4:00 a.m. this morning, Downtown Los Angeles has recorded 0.16
inches for the storm, bumping the water year total to 105% of normal.

As a result of the westerly flow, snow levels are currently
high, but one of the interesting facets of last Friday's storm was the possibility
of very low elevation snow. A NWS Winter Weather Advisory issued February 25 for the
Santa Monica Mountains Recreation Area forecast the snow level to drop overnight from
above 3000' to between 1000' and 1500'. Snow accumulations from 1 to 3 inches were
expected. Some low elevation post frontal showers of graupel or snow were reported
in the east San Fernando Valley and La Crescenta Saturday afternoon, but based
on the conditions on Sandstone Peak (el. 3111'), the snow anticipated in the SMMRA
did not occur. It was an especially challenging forecast, pitting pre-frontal warm
air advection, against post-frontal cold air advection, falling humidity, and fluctuating
regions of snow growth and omega.

Developed in part to help
forecasters deal with lake effect snow, BUFKIT includes a number of special features
for snow forecasting and visualization. For example, following are two time-height
cross sections generated by BUFKIT from NAM data for VNY (Van Nuys) from 4:00 p.m.
Friday, February 25. The elevation for the Bourgoiun precipitation type analysis for
each cross section has been raised to 2711 feet MSL. The first
BUFKIT cross section shows snow growth, omega, temperature, and the projected
precipitation amount and type. The second
cross section shows the same parameters, but with relative humidity instead of
omega. The purple and yellow rectilinear contours are snow growth, and the red and
blue contours are omega. The green bars are rain amounts, and the blue bars snow.
Some of the things to note in these cross sections are the omega/snow growth "cross
hair," freezing level, and rapid decrease in humidity with the frontal passage.

What the discrete NAM forecast can't show is the variability
of the forecast situation. In its most recent release BUFKIT added support for SREF
and eWRF ensembles. When combined with BUFKIT's precipitation type and other tools,
ensemble forecasts can provide much additional information and insight. In this case
eWRF ensemble members for VNY exhibited widely varying thermal profiles, regions of
snow growth, omega, and humidity. BUFKIT's Bourgoiun
precipitation type analysis for the eWRF ensemble members at 8:00 a.m. Saturday
morning showed freezing levels as high as 2882' and as low as 1176'. The pattern of
post-frontal precipitation was also quite variable.

More information concerning Southern California weather
can be found using our WEATHER LINKS page.

Southern California Weather Notes Copyright 2000-2017 Gary Valle. All Rights Reserved.
Los Angeles Rainfall At 105% of Normal for the Water Year. BUFKIT Los Angeles Snow Forecast Visualization.http://www.sierraphotography.com/wxnotes/PermaLink,guid,8a13a4c8-1de9-40d5-a4bb-fccd308dd907.aspxhttp://www.sierraphotography.com/wxnotes/LosAngelesRainfallAt105OfNormalForTheWaterYearBUFKITLosAngelesSnowForecastVisualization.aspx
Thu, 03 Mar 2011 16:58:48 GMT
<div id="mainwx">
<div class="fltlft">
<p align="center">
<a title="BUFKIT Bourgoiun precipitation type analysis and sounding for eWRF Ensembles at VNY at 8:00 am 02/26/11" href="wxdata1011/ewrf_vny_energy_022611_12zb.png" rel="wximage" target="_blank"> <img border="0" src="wxdata1011/ewrf_vny_energy_022611_12zc.png" width="350" height="368" /> </a> <img alt="Click" src="images/click.gif" width="16" height="34" />
<br />
<span class="fontxxsmall">BUFKIT Bourgoiun Precipitation Type Analysis<br />
For eWRF Ensembles for VNY at 8:00 am 02/26/11</span>
</p>
</div>
<p>
<span class="dropcap">T</span>he wetter ensemble member forecasts prevailed in last
Friday's and Saturday's rain and snow event. Downtown Los Angeles recorded 1.20 inches
for the storm. This brought the water year total to 15.78 inches, which is about 104%
of normal. Although this might seem unusual in a La Nina influenced rain season, during <a href="http://www.sierraphotography.com/wxnotes/HowDoesTheLaNinaOf201011CompareToOtherColdENSOEpisodesSince1949.aspx" target="_blank">two
of the strongest La Ninas in the past 60 years</a> -- 1955-56 and 1973-74 -- Los Angeles
recorded 99% and 106% of normal rainfall. Here's an archived copy of a <a href="wxdata1011/RRMLOX022611_2200PST.pdf" target="_blank">NWS
tabulation of some rainfall totals</a> from around the area from early Friday, February
25, to 10:00 p.m. Saturday, February 26.
</p>
<p>
<span class="dropcap">T</span>he NAM and GFS, as well as the SREF and eWRF ensembles,
had a tough time forecasting the rainfall produced by our current scenario -- a relatively
shallow, moist westerly flow accompanied by <a href="wxdata1011/nam_300_000s_030311_00zb.gif" rel="wximage" target="_blank">modest
jet stream dynamics</a>. As this <a title="BUFKIT cross section of wind speed and plot of accumulated precipitation." href="wxdata1011/ewrf_vny_jet_030311_00zb.png" rel="wximage" target="_blank">BUFKIT
time-height cross section</a> shows, the wettest eWRF ensemble member depicted a 125
kt jet max overhead, suggesting the models had some difficulty in forecasting the
structure and strength of the jet. At best, the models forecast a few hundredths of
an inch of rain in the Los Angeles area, but the most recent <a href="wxdata1011/RRMLOX030311_0436PST.pdf" target="_blank">NWS
tabulation of rainfall totals</a> for the event lists many stations with between 0.1
and 0.25 inch. As of 4:00 a.m. this morning, Downtown Los Angeles has recorded 0.16
inches for the storm, bumping the water year total to 105% of normal.
</p>
<p>
<span class="dropcap">A</span>s a result of the westerly flow, snow levels are currently
high, but one of the interesting facets of last Friday's storm was the possibility
of very low elevation snow. A NWS Winter Weather Advisory issued February 25 for the
Santa Monica Mountains Recreation Area forecast the snow level to drop overnight from
above 3000' to between 1000' and 1500'. Snow accumulations from 1 to 3 inches were
expected. Some low elevation post frontal showers of graupel or snow were reported
in the east San Fernando Valley and La Crescenta Saturday afternoon, but <a href="http://www.photographyontherun.com/LookingForSnowInTheSantaMonicaMountains.aspx" target="_blank">based
on the conditions on Sandstone Peak</a> (el. 3111'), the snow anticipated in the SMMRA
did not occur. It was an especially challenging forecast, pitting pre-frontal warm
air advection, against post-frontal cold air advection, falling humidity, and fluctuating
regions of snow growth and omega.
</p>
<p>
<span class="dropcap">D</span>eveloped in part to <a href="http://www.erh.noaa.gov/er/buf/respap1.htm" target="_blank">help
forecasters deal with lake effect snow</a>, BUFKIT includes a number of special features
for snow forecasting and visualization. For example, following are two time-height
cross sections generated by BUFKIT from NAM data for VNY (Van Nuys) from 4:00 p.m.
Friday, February 25. The elevation for the Bourgoiun precipitation type analysis for
each cross section has been raised to 2711 feet MSL. The <a title="BUFKIT cross section of snow growth, omega, temperature, and the precipitation amount and type. Elevation raised to 2711 ft MSL." href="wxdata1011/nam_vny_snow_omega_022611_00zb.png" rel="wximage" target="_blank">first
BUFKIT cross section</a> shows snow growth, omega, temperature, and the projected
precipitation amount and type. The <a title="BUFKIT cross section of snow growth, relative humidity, temperature, and the precipitation amount and type. Elevation raised to 2711 ft MSL." href="wxdata1011/nam_vny_snow_relhum_022611_00zb.png" rel="wximage" target="_blank">second
cross section</a> shows the same parameters, but with relative humidity instead of
omega. The purple and yellow rectilinear contours are snow growth, and the red and
blue contours are omega. The green bars are rain amounts, and the blue bars snow.
Some of the things to note in these cross sections are the omega/snow growth "cross
hair," freezing level, and rapid decrease in humidity with the frontal passage.
</p>
<p>
<span class="dropcap">W</span>hat the discrete NAM forecast can't show is the variability
of the forecast situation. In its most recent release BUFKIT added support for SREF
and eWRF ensembles. When combined with BUFKIT's precipitation type and other tools,
ensemble forecasts can provide much additional information and insight. In this case
eWRF ensemble members for VNY exhibited widely varying thermal profiles, regions of
snow growth, omega, and humidity. BUFKIT's <a title="BUFKIT Bourgoiun precipitation type analysis and sounding for eWRF Ensembles at VNY at 8:00 am 02/26/11" href="wxdata1011/ewrf_vny_energy_022611_12zb.png" rel="wximage" target="_blank">Bourgoiun
precipitation type analysis</a> for the eWRF ensemble members at 8:00 a.m. Saturday
morning showed freezing levels as high as 2882' and as low as 1176'. The pattern of
post-frontal precipitation was also quite variable.
</p>
<p>
<span class="dropcap">M</span>ore information concerning Southern California weather
can be found using our <a href="weatherlinks.htm">WEATHER LINKS</a> page.
</p>
<div class="clearfloat">
</div>
</div>
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<br />
<hr />Southern California Weather Notes Copyright 2000-2017 Gary Valle. All Rights Reserved.climateLa NinaLos Angeles rainfallweatherhttp://www.sierraphotography.com/wxnotes/Trackback.aspx?guid=8bafd627-9882-4869-8f1d-9d575718844ehttp://www.sierraphotography.com/wxnotes/pingback.aspxhttp://www.sierraphotography.com/wxnotes/PermaLink,guid,8bafd627-9882-4869-8f1d-9d575718844e.aspxGary Valle

The rainfall totals from Friday's and Saturday's systems
were generally a little below the 2 inches forecast, but it was still enough to boost
the water year rainfall total for Downtown Los Angeles to 14.58 inches. This is about
96% of the normal water year total of 15.14 inches. The water year extends from July
1 to June 30, so we still have four months to receive the 0.56 inch of rain that would
put us at 100%. Here's an archived copy of a NWS
tabulation of some rainfall totals from around the area from early Thursday morning
to 10:00 a.m. Sunday.

Southern California's wet weather pattern didn't extend
into this week as it looked like it might. The upper low that might have produced
the rainfall is now forecast to stay offshore. At the moment it looks like it will
mainly result in some clouds as it moves down the coast today through Wednesday. Rain
chances increase near the end of the week and into the weekend as an upper low and
trough work
down the West Coast. Ensemble members vary quite a bit on the track of the upper
low, with some solutions wetter in Southern California than others. We'll see!

More information concerning Southern California weather
can be found using our WEATHER LINKS page.

Southern California Weather Notes Copyright 2000-2017 Gary Valle. All Rights Reserved.
Los Angeles Rainfall at 96% of Normal for the Water Year. Upper Low Skirts Coast. Rain at End of the Week?http://www.sierraphotography.com/wxnotes/PermaLink,guid,8bafd627-9882-4869-8f1d-9d575718844e.aspxhttp://www.sierraphotography.com/wxnotes/LosAngelesRainfallAt96OfNormalForTheWaterYearUpperLowSkirtsCoastRainAtEndOfTheWeek.aspx
Mon, 21 Feb 2011 22:28:03 GMT
<div id="mainwx">
<div class="fltlft">
<p align="center">
<a title="Experimental HPC 6-Hour Probabilistic Precipitation Guidance for the 6 hr. period ending 4:00 pm Tuesday" href="wxdata1011/p06i_pqpf_ge001_2011022118f030b.gif" rel="wximage" target="_blank"> <img border="0" src="wxdata1011/p06i_pqpf_ge001_2011022118f030c.gif" width="350" height="262" /> </a> <img alt="Click" src="images/click.gif" width="16" height="34" />
<br />
<span class="fontxxsmall">Experimental HPC 6-Hour Probabilistic Precipitation Guidance<br />
For the 6 Hour Period Ending 4:00 p.m. Tuesday</span>
</p>
</div>
<p>
<span class="dropcap">T</span>he rainfall totals from Friday's and Saturday's systems
were generally a little below the 2 inches forecast, but it was still enough to boost
the water year rainfall total for Downtown Los Angeles to 14.58 inches. This is about
96% of the normal water year total of 15.14 inches. The water year extends from July
1 to June 30, so we still have four months to receive the 0.56 inch of rain that would
put us at 100%. Here's an archived copy of a <a href="wxdata1011/RRMLOX022011_1000PST.pdf" target="_blank">NWS
tabulation of some rainfall totals</a> from around the area from early Thursday morning
to 10:00 a.m. Sunday.
</p>
<p>
<span class="dropcap">S</span>outhern California's wet weather pattern didn't extend
into this week as it looked like it might. The upper low that might have produced
the rainfall is now forecast to stay offshore. At the moment it looks like it will
mainly result in some clouds as it moves down the coast today through Wednesday. Rain
chances increase near the end of the week and into the weekend as an upper low and
trough <a href="wxdata1011/gfs_500_120m_022111_12zb.gif" rel="wximage" target="_blank">work
down the West Coast</a>. Ensemble members vary quite a bit on the track of the upper
low, with some solutions wetter in Southern California than others. We'll see!
</p>
<p>
<span class="dropcap">M</span>ore information concerning Southern California weather
can be found using our <a href="weatherlinks.htm">WEATHER LINKS</a> page.
</p>
<div class="clearfloat">
</div>
</div>
<img width="0" height="0" src="http://www.sierraphotography.com/wxnotes/aggbug.ashx?id=8bafd627-9882-4869-8f1d-9d575718844e" />
<br />
<hr />Southern California Weather Notes Copyright 2000-2017 Gary Valle. All Rights Reserved.Los Angeles rainfallprecipitation outlookweatherhttp://www.sierraphotography.com/wxnotes/Trackback.aspx?guid=d612570b-9c5a-4178-b593-e4c96030221fhttp://www.sierraphotography.com/wxnotes/pingback.aspxhttp://www.sierraphotography.com/wxnotes/PermaLink,guid,d612570b-9c5a-4178-b593-e4c96030221f.aspxGary Valle

The transition from a persistent West Coast ridge to
a West Coast trough occurred on Monday more or less as forecast by medium range guidance
back on February 5. A series of systems and impulses riding up and over a high amplitude
Eastern Pacific ridge are expected to continue to produce cool, blustery weather in
Southern California with periods of showers and rain into next week.

Precipitation on Valentine's Day was generally limited
to areas north of the Los Angeles basin, but was a little more widespread late Monday
night into Tuesday morning, with a number of stations in the Los Angeles area recording
a few hundredths of an inch of rain.

Wednesday's system was much more energetic. Because of
the convective nature of the precipitation, rainfall amounts were extremely variable,
ranging 0.25 inch or less to 1.0 inch or more. Downtown Los Angeles (USC) recorded
0.65 inch of rain for the storm, bringing the water year total for Los Angeles to
13.14 inches. This is well above normal for the date, and about 87% of normal for
the water year. Here's an archived copy of a NWS
tabulation of some rainfall totals for the period 4:00 p.m. Tuesday to 4:00 a.m.
Thursday.

Los Angeles only needs about 2 more inches of rain to
top the 100% mark for the water year, and it looks like we could get most of that
Friday and Saturday. BUFKIT
analysis of 12z NAM data for Van Nuys indicates about 1.6 inches of rain Friday
into Saturday, and then another 0.5 inch Saturday night. The HPC
3-day Quantitative Precipitation Forecast for the period ending 4:00 a.m. Sunday
also indicates about 2.0 inches of rain in Southern California. This morning's 09z
SREF puts the probability
of more than 1.0 inch rain for the 24 hour period ending 1:00 p.m. Saturday at
about 70%.

Temperature data at the surface and at depth in the equatorial
Pacific suggest the La Nina is moderating. The tough question is whether warming will
continue into the NH summer, with neutral ENSO conditions prevailing as we move into
autumn; or if the ENSO cycle will swing back toward a La Nina state. Since 1949, about
half of the first year La
Nina episodes continued into a second or third year. At the moment the majority
of computer models favor a transition to ENSO neutral or warm conditions by July 2011.
Here is a compilation
of ENSO Forecasts from the IRI
ENSO Quick Look for February 17, 2011. We'll see!

More information concerning Southern California weather
can be found using our WEATHER LINKS page.

Southern California Weather Notes Copyright 2000-2017 Gary Valle. All Rights Reserved.
Los Angeles Rainfall at 87% of Normal for the Water Year and Counting. More Rain on the Way. La Nina Moderating - Will It Rebound?http://www.sierraphotography.com/wxnotes/PermaLink,guid,d612570b-9c5a-4178-b593-e4c96030221f.aspxhttp://www.sierraphotography.com/wxnotes/LosAngelesRainfallAt87OfNormalForTheWaterYearAndCountingMoreRainOnTheWayLaNinaModeratingWillItRebound.aspx
Thu, 17 Feb 2011 21:31:48 GMT
<div id="mainwx">
<div class="fltlft">
<p align="center">
<a title="HPC 3-Day Precipitation Forecast for period ending Sunday morning. Lighter green contour is 2.0 inches." href="wxdata1011/hpc-3dayqpf_021711_0953b.png" rel="wximage" target="_blank"> <img border="0" src="wxdata1011/hpc-3dayqpf_021711_0953c.png" width="350" height="263" /> </a> <img alt="Click" src="images/click.gif" width="16" height="34" />
<br />
<span class="fontxxsmall">HPC 3-Day Precipitation Forecast<br />
For the Period Ending 4:00 a.m. Sunday Morning</span>
</p>
</div>
<p>
<span class="dropcap">T</span>he transition from a persistent West Coast ridge to
a West Coast trough occurred on Monday more or less as forecast by medium range guidance
back on February 5. A series of systems and impulses riding up and over a high amplitude
Eastern Pacific ridge are expected to continue to produce cool, blustery weather in
Southern California with periods of showers and rain into next week.
</p>
<p>
<span class="dropcap">P</span>recipitation on Valentine's Day was generally limited
to areas north of the Los Angeles basin, but was a little more widespread late Monday
night into Tuesday morning, with a number of stations in the Los Angeles area <a href="wxdata1011/RRMLOX021511_1629PST.pdf" target="_blank">recording
a few hundredths of an inch of rain</a>.
</p>
<p>
<span class="dropcap">W</span>ednesday's system was much more energetic. Because of
the convective nature of the precipitation, rainfall amounts were extremely variable,
ranging 0.25 inch or less to 1.0 inch or more. Downtown Los Angeles (USC) recorded
0.65 inch of rain for the storm, bringing the water year total for Los Angeles to
13.14 inches. This is well above normal for the date, and about 87% of normal for
the water year. Here's an archived copy of a <a href="wxdata1011/RRMLOX021711_0450PST.pdf" target="_blank">NWS
tabulation of some rainfall totals</a> for the period 4:00 p.m. Tuesday to 4:00 a.m.
Thursday.
</p>
<p>
<span class="dropcap">L</span>os Angeles only needs about 2 more inches of rain to
top the 100% mark for the water year, and it looks like we could get most of that
Friday and Saturday. <a href="wxdata1011/BUFKIT_NAM_VNY_021711_12zb.png" rel="wximage" target="_blank">BUFKIT
analysis of 12z NAM data</a> for Van Nuys indicates about 1.6 inches of rain Friday
into Saturday, and then another 0.5 inch Saturday night. The <a href="wxdata1011/hpc-3dayqpf_021711_0953b.png" rel="wximage" target="_blank">HPC
3-day Quantitative Precipitation Forecast</a> for the period ending 4:00 a.m. Sunday
also indicates about 2.0 inches of rain in Southern California. This morning's 09z
SREF puts the <a href="wxdata1011/sref_apcp24h_pr1_60_021711_09zb.gif" rel="wximage" target="_blank">probability
of more than 1.0 inch rain</a> for the 24 hour period ending 1:00 p.m. Saturday at
about 70%.
</p>
<p>
<span class="dropcap">T</span>emperature data at the surface and at depth in the equatorial
Pacific suggest the La Nina is moderating. The tough question is whether warming will
continue into the NH summer, with neutral ENSO conditions prevailing as we move into
autumn; or if the ENSO cycle will swing back toward a La Nina state. Since 1949, about
half of the first year <a href="http://www.sierraphotography.com/wxnotes/HowDoesTheLaNinaOf201011CompareToOtherColdENSOEpisodesSince1949.aspx" target="_blank">La
Nina episodes</a> continued into a second or third year. At the moment the majority
of computer models favor a transition to ENSO neutral or warm conditions by July 2011.
Here is a <a href="wxdata1011/IRI_ENSO_forecasts_021611b.gif" rel="wximage" target="_blank">compilation
of ENSO Forecasts</a> from the <a href="http://iri.columbia.edu/climate/ENSO/currentinfo/QuickLook.html" target="_blank">IRI
ENSO Quick Look</a> for February 17, 2011. We'll see!
</p>
<p>
<span class="dropcap">M</span>ore information concerning Southern California weather
can be found using our <a href="weatherlinks.htm">WEATHER LINKS</a> page.
</p>
<div class="clearfloat">
</div>
</div>
<img width="0" height="0" src="http://www.sierraphotography.com/wxnotes/aggbug.ashx?id=d612570b-9c5a-4178-b593-e4c96030221f" />
<br />
<hr />Southern California Weather Notes Copyright 2000-2017 Gary Valle. All Rights Reserved.climateLa NinaLos Angeles rainfallprecipitation outlookQPF forecastweatherhttp://www.sierraphotography.com/wxnotes/Trackback.aspx?guid=d57f7b50-9c70-44ea-93b8-079f7ad2b772http://www.sierraphotography.com/wxnotes/pingback.aspxhttp://www.sierraphotography.com/wxnotes/PermaLink,guid,d57f7b50-9c70-44ea-93b8-079f7ad2b772.aspxGary Valle

Although the Pacific jet did expand as anticipated through
about January 27, and then retract around January
29, leading to a upper
low off the California coast, it wasn't the discontinuous ridge regression which
had been hoped for -- or the change in pattern that would open the door to Pacific
storms wishing to visit sunny Southern California.

The area did manage to get a bit of rainfall out of the
system. Downtown Los Angeles (USC) recorded 0.21 inch on Sunday, bringing the rainfall
total for January up to a paltry 0.79 inches, which is more than 2.5 inches below
normal for the month. At this point Downtown Los Angeles remains almost 5 inches above
normal for the water year (July 1 to June 30), but with each dry day that cushion
grows a little smaller. Here's an archived copy of a NWS
tabulation of some rainfall totals from last Sunday's storm.

Over the next two weeks, the MJO signal currently propagating
across the western Pacific is forecast to destructively
interfere with the La Nina base state, suppressing convection in the Indian Ocean
and Indonesia and enhancing convection near the dateline. This is forecast to result
in a transition from upper tropospheric anomalous cyclones to anticyclones near the
dateline, and an extension of the East Asian/Pacific jet. These circulation changes
may eventually lead to a retrogression of our persistent West Coast ridge, or perhaps
a breakthrough of the westerlies underneath the highly amplified ridge.

The key word here is eventually. Over the next
week or so, the extending
Pacific jet is forecast to reamplify the ridge over the West Coast. But at some
point, perhaps near the beginning of February, destructive interference in the Western
Pacific will dwindle and convection in the Indian Ocean will strengthen. This should
result in retraction of the Pacific jet, and possibly, a West Coast trough. The 240
hr forecast of the 12z ECMWF hinted at this possibility, as did the 18z GFS. We'll
see!

After starting out cold and wet, the weather this January
in Southern California, and much of the state, has been warm and dry. Monday, Pierce
College in Woodland Hills hit a high of 88°F, and Downtown Los Angeles (USC) 84°F.
So far this January, only 0.58 of rain has been recorded at Downtown Los Angeles (USC),
which is a little less than one-third of normal for the month. However, because of
our prodigious December rainfall the water year total at Los Angeles is currently
6.5 inches above the normal for the date of 5.78 inches.

More information concerning Southern California weather
can be found using our WEATHER LINKS page.

Southern California Weather Notes Copyright 2000-2017 Gary Valle. All Rights Reserved.
MJO Could Force Pattern Change That Eventually Results in More California Rain. Mammatus Clouds Over the San Fernando Valley.http://www.sierraphotography.com/wxnotes/PermaLink,guid,b2fc72dc-5135-403d-8263-cdcacec28311.aspxhttp://www.sierraphotography.com/wxnotes/MJOCouldForcePatternChangeThatEventuallyResultsInMoreCaliforniaRainMammatusCloudsOverTheSanFernandoValley.aspx
Fri, 21 Jan 2011 03:25:42 GMT
<div id="mainwx">
<div class="fltlft">
<p align="center">
<a title="Extended Pacific Jet and Highly Amplified Ridge Forecast by 12z GFS" href="wxdata1011/gfs_250_084s_012011b.gif" rel="wximage" target="_blank"> <img border="0" src="wxdata1011/gfs_250_084s_012011c.gif" width="350" height="263" /> </a> <img alt="Click" src="images/click.gif" width="16" height="34" />
<br />
<span class="fontxxsmall">Extended Pacific Jet and Resulting Mega-Ridge<br />
GFS Forecast for Sunday Afternoon</span>
</p>
</div>
<p>
<span class="dropcap">O</span>ver the next two weeks, the MJO signal currently <a href="wxdata1011/mjo_Last40days011911b.gif" rel="wximage" target="_blank">propagating
across the western Pacific</a> is forecast to <a href="wxdata1011/bmrc_mjo_anom_uv200_011911b.gif" target="_blank">destructively
interfere with the La Nina base state</a>, suppressing convection in the Indian Ocean
and Indonesia and enhancing convection near the dateline. This is forecast to result
in a transition from upper tropospheric anomalous cyclones to anticyclones near the
dateline, and an extension of the East Asian/Pacific jet. These circulation changes
may eventually lead to a retrogression of our persistent West Coast ridge, or perhaps
a breakthrough of the westerlies underneath the highly amplified ridge.
</p>
<p>
<span class="dropcap">T</span>he key word here is <i>eventually</i>. Over the next
week or so, the <a href="wxdata1011/gfs_250_084s_012011b.gif" rel="wximage" target="_blank">extending
Pacific jet is forecast to reamplify the ridge</a> over the West Coast. But at some
point, perhaps near the beginning of February, destructive interference in the Western
Pacific will dwindle and convection in the Indian Ocean will strengthen. This should
result in retraction of the Pacific jet, and possibly, a West Coast trough. The 240
hr forecast of the 12z ECMWF hinted at this possibility, as did the 18z GFS. We'll
see!
</p>
<p>
<span class="dropcap">A</span>fter starting out cold and wet, the weather this January
in Southern California, and much of the state, has been warm and dry. Monday, Pierce
College in Woodland Hills hit a high of 88°F, and Downtown Los Angeles (USC) 84°F.
So far this January, only 0.58 of rain has been recorded at Downtown Los Angeles (USC),
which is a little less than one-third of normal for the month. However, because of
our prodigious December rainfall the water year total at Los Angeles is currently
6.5 inches above the normal for the date of 5.78 inches.
</p>
<p>
<span class="dropcap">E</span>arlier this month I photographed these <a href="http://www.photographyontherun.com/prun.asp?id=624" target="_blank">mid-level
mammatus clouds over the western San Fernando Valley</a>. They were produced by the
moisture and dynamics associated with a closed upper level low that was about 390
miles WSW of Los Angeles. To see how the clouds evolved and more about the scenario
at the time, see <a href="http://www.photographyontherun.com/MammatusCloudsOverTheSanFernandoValley.aspx" target="_blank">this
post on PhotographyontheRun.com</a>.
</p>
<p>
<span class="dropcap">M</span>ore information concerning Southern California weather
can be found using our <a href="weatherlinks.htm">WEATHER LINKS</a> page.
</p>
<div class="clearfloat">
</div>
</div>
<img width="0" height="0" src="http://www.sierraphotography.com/wxnotes/aggbug.ashx?id=b2fc72dc-5135-403d-8263-cdcacec28311" />
<br />
<hr />Southern California Weather Notes Copyright 2000-2017 Gary Valle. All Rights Reserved.climateLos Angeles rainfallMadden-Julian Oscillation (MJO)precipitation outlookweatherhttp://www.sierraphotography.com/wxnotes/Trackback.aspx?guid=e101419b-5a46-406e-a86c-c48ae9762054http://www.sierraphotography.com/wxnotes/pingback.aspxhttp://www.sierraphotography.com/wxnotes/PermaLink,guid,e101419b-5a46-406e-a86c-c48ae9762054.aspxGary Valle

Up until a couple of days ago it looked like there might
be some damp weather for the Rose Parade and even a better chance for the Rose Bowl
game. An upper level low was the culprit, and they are notoriously difficult to model
and forecast. The low is out there, it's just
further to the north, and so is the rain.

How likely is rain on New Year's Day in Pasadena? Here's
a plot generated
on the Western Regional Climate Center web site, that shows the probability of
various amounts of rain in a 1-day period at Pasadena. The probability of measurable
rain (0.01 inch) in a 24 hour period around January 1 is about 20%, or about 1 in
5. As the rainfall amounts increase, the probability drops. The chance of 1.0 inch
of rain is about 4%, or 1 in 25. Keep in mind that the probabilities indicated are
for a 24 hour period. The chance of rain for the relatively short two hour duration
of the Rose Parade is quite a bit less -- as history demonstrates.

Wednesday's cold
front, the latest in our series of surprisingly frequent December weather systems,
upped the water year rainfall total at Downtown Los Angeles (USC) to 11.70 inches.
As of December 31, L.A.'s rainfall total is about 8 inches above normal, and more
than three times the normal amount of rainfall for the water year to date. For the
first six months of the 2010-11 water year, the rainfall total for Downtown Los Angeles
is the fourth wettest in the 133 years that records have been kept. The water year
starts on July 1 and ends June 30.

And we're not done yet. In a normal year, Downtown Los
Angeles records about two-thirds of its annual rainfall in the months of January,
February and March. This amounts to a little over 10 inches of rain. Depending on
how you look at the data, rainfall for Downtown Los Angeles during a La Nina episode
is usually about 70%-80% of normal. In addition, the composite
plus trend plot for Jan-Feb-Mar precipitation anomaly (from CPC) is particularly
dry in coastal Southern California, indicating negative anomalies in excess of 3 inches,
with a high frequency of occurrence. Even so, it looks like Los Angeles has a good
chance of exceeding the normal amount of annual rainfall of 15.14 inches. All we need
before June 30 is another 3.45 inches!

The upper level low postponed on account of the Rose
Parade, but due in tomorrow, should help with that. BUFKIT
analysis of this morning's WRF ensembles projects anywhere from 0.6 inch to 0.9
inch of rain at Van Nuys through early Monday morning. The 18z NAM isn't as wet, projecting
about 0.4 inch. The models are still having difficulties with the forecast, and slight
changes in the position and behavior of the upper low could have a significant impact
on the amount of rainfall. We'll see!

More information concerning Southern California weather
can be found using our WEATHER LINKS page.

Southern California Weather Notes Copyright 2000-2017 Gary Valle. All Rights Reserved.
Pasadena Precipitation Probabilities. Fourth Wettest Water Year in Los Angeles To Date. How Much More Rain?http://www.sierraphotography.com/wxnotes/PermaLink,guid,e101419b-5a46-406e-a86c-c48ae9762054.aspxhttp://www.sierraphotography.com/wxnotes/PasadenaPrecipitationProbabilitiesFourthWettestWaterYearInLosAngelesToDateHowMuchMoreRain.aspx
Sat, 01 Jan 2011 23:13:31 GMT
<div id="mainwx">
<div class="fltlft">
<p align="center">
<a title="WRF Ensembles Projected Precipitation through early Monday morning. (BUFKIT)" href="wxdata1011/eWRFprecip010111_12zb.png" rel="wximage" target="_blank"> <img border="0" src="wxdata1011/eWRFprecip010111_12zc.png" width="350" height="227" /> </a> <img alt="Click" src="images/click.gif" width="16" height="34" />
<br />
<span class="fontxxsmall">WRF Ensembles Projected Precipitation<br />
Through Monday, January 3, 2011 at 4:00 a.m.</span>
</p>
</div>
<p>
<span class="dropcap">U</span>p until a couple of days ago it looked like there might
be some damp weather for the Rose Parade and even a better chance for the Rose Bowl
game. An upper level low was the culprit, and they are notoriously difficult to model
and forecast. The low is out there, it's <a href="wxdata1011/goes11ir010111_2100zb.gif" rel="wximage" target="_blank">just
further to the north</a>, and so is the rain.
</p>
<p>
<span class="dropcap">H</span>ow likely is rain on New Year's Day in Pasadena? Here's
a <a href="wxdata1011/precipprob1daypasb.png" rel="wximage" target="_blank">plot generated
on the Western Regional Climate Center web site</a>, that shows the probability of
various amounts of rain in a 1-day period at Pasadena. The probability of measurable
rain (0.01 inch) in a 24 hour period around January 1 is about 20%, or about 1 in
5. As the rainfall amounts increase, the probability drops. The chance of 1.0 inch
of rain is about 4%, or 1 in 25. Keep in mind that the probabilities indicated are
for a 24 hour period. The chance of rain for the relatively short two hour duration
of the Rose Parade is quite a bit less -- as history demonstrates.
</p>
<p>
<span class="dropcap">W</span>ednesday's <a href="wxdata1011/goes11ir122910_1400zb.gif" rel="wximage" target="_blank">cold
front</a>, the latest in our series of surprisingly frequent December weather systems,
upped the water year rainfall total at Downtown Los Angeles (USC) to 11.70 inches.
As of December 31, L.A.'s rainfall total is about 8 inches above normal, and more
than three times the normal amount of rainfall for the water year to date. For the
first six months of the 2010-11 water year, the rainfall total for Downtown Los Angeles
is the fourth wettest in the 133 years that records have been kept. The water year
starts on July 1 and ends June 30.
</p>
<p>
<span class="dropcap">A</span>nd we're not done yet. In a normal year, Downtown Los
Angeles records about two-thirds of its annual rainfall in the months of January,
February and March. This amounts to a little over 10 inches of rain. Depending on
how you look at the data, rainfall for Downtown Los Angeles during a La Nina episode
is usually about 70%-80% of normal. In addition, the <a href="http://www.sierraphotography.com/wxnotes/wxdata1011/cpc_lanina.jfm.precip.gif" rel="wximage" target="_blank">composite
plus trend plot for Jan-Feb-Mar precipitation anomaly</a> (from CPC) is particularly
dry in coastal Southern California, indicating negative anomalies in excess of 3 inches,
with a high frequency of occurrence. Even so, it looks like Los Angeles has a good
chance of exceeding the normal amount of annual rainfall of 15.14 inches. All we need
before June 30 is another 3.45 inches!
</p>
<p>
<span class="dropcap">T</span>he upper level low postponed on account of the Rose
Parade, but due in tomorrow, should help with that. <a href="wxdata1011/eWRFprecip010111_12zb.png" rel="wximage" target="_blank">BUFKIT
analysis of this morning's WRF ensembles</a> projects anywhere from 0.6 inch to 0.9
inch of rain at Van Nuys through early Monday morning. The 18z NAM isn't as wet, projecting
about 0.4 inch. The models are still having difficulties with the forecast, and slight
changes in the position and behavior of the upper low could have a significant impact
on the amount of rainfall. We'll see!
</p>
<p>
<span class="dropcap">M</span>ore information concerning Southern California weather
can be found using our <a href="weatherlinks.htm">WEATHER LINKS</a> page.
</p>
<div class="clearfloat">
</div>
</div>
<img width="0" height="0" src="http://www.sierraphotography.com/wxnotes/aggbug.ashx?id=e101419b-5a46-406e-a86c-c48ae9762054" />
<br />
<hr />Southern California Weather Notes Copyright 2000-2017 Gary Valle. All Rights Reserved.La NinaLos Angeles rainfallprecipitation outlookweatherhttp://www.sierraphotography.com/wxnotes/Trackback.aspx?guid=76d90475-b6b0-458c-ba94-0c2fb6d71b07http://www.sierraphotography.com/wxnotes/pingback.aspxhttp://www.sierraphotography.com/wxnotes/PermaLink,guid,76d90475-b6b0-458c-ba94-0c2fb6d71b07.aspxGary Valle

WSI Composite Radar
December 25, 2010 at 8:00 p.m.

The strong cold front that swept through Southern California
Christmas night resulted in 0.90 inch of rain at Downtown Los Angeles (USC), increasing
December's rainfall total to 9.67 inches. This makes December 2010 the wettest December
in 121 years (since 1889), and the second wettest December since recordkeeping began
in 1877.

Rainfall totals from last night's fast moving front generally
ranged from about 0.4 inch to 0.9 inch. Here's an archived copy of a Precipitation
Summary from the NWS Los Angeles/Oxnard with some rainfall totals from around
the area.

This morning's model runs continue to forecast more rain
for Wednesday. The 12z NAM projects about 0.5 inch at LAX during the day Wednesday.
The 09z SREF puts the probability of more than 0.25 inch of rain in the Los Angeles
area at about 50% for the 24 hour period ending 4:00 p.m. Wednesday afternoon.

Depending on how much rain we get Wednesday, for the
first six months of the 2010-11 water year (July 1 to December 31), the rainfall total
for Downtown Los Angeles will likely rank as the fourth or fifth wettest in the 133
years that records have been kept.

In the medium range outlook, the 12z GFS and 12z ECMWF differ
in how they handle an upper level low that they forecast to develop off the California
coast New Year's morning. The 12z GFS is quite wet New Year's weekend, but it's too
early to put much credence in that forecast. We'll see!

More information concerning Southern California weather
can be found using our WEATHER LINKS page.

Southern California Weather Notes Copyright 2000-2017 Gary Valle. All Rights Reserved.
Wettest December in Los Angeles in 121 Years! Rain New Year's Weekend?http://www.sierraphotography.com/wxnotes/PermaLink,guid,76d90475-b6b0-458c-ba94-0c2fb6d71b07.aspxhttp://www.sierraphotography.com/wxnotes/WettestDecemberInLosAngelesIn121YearsRainNewYearsWeekend.aspx
Sun, 26 Dec 2010 22:01:15 GMT
<div id="mainwx">
<div class="fltlft">
<p align="center">
<a title="WSI Composite Radar for December 25, 2010 at 8:00 p.m." href="wxdata1011/wsicompradar_122610_0400zb.gif" rel="wximage"> <img src="wxdata1011/wsicompradar_122610_0400zc.gif" width="350" height="226" border="0" /> </a> <img alt="Click" src="images/click.gif" width="16" height="34" />
<br />
<span class="fontxxsmall">WSI Composite Radar<br />
December 25, 2010 at 8:00 p.m.</span>
</p>
</div>
<p>
<span class="dropcap">T</span>he strong cold front that swept through Southern California
Christmas night resulted in 0.90 inch of rain at Downtown Los Angeles (USC), increasing
December's rainfall total to 9.67 inches. This makes December 2010 the wettest December
in 121 years (since 1889), and the second wettest December since recordkeeping began
in 1877.
</p>
<p>
<span class="dropcap">R</span>ainfall totals from last night's fast moving front generally
ranged from about 0.4 inch to 0.9 inch. Here's an archived copy of a <a href="wxdata1011/RRMLOX122610_0426PST.pdf" target="_blank">Precipitation
Summary</a> from the NWS Los Angeles/Oxnard with some rainfall totals from around
the area.
</p>
<p>
<span class="dropcap">T</span>his morning's model runs continue to forecast more rain
for Wednesday. The 12z NAM projects about 0.5 inch at LAX during the day Wednesday.
The 09z SREF puts the probability of more than 0.25 inch of rain in the Los Angeles
area at about 50% for the 24 hour period ending 4:00 p.m. Wednesday afternoon.
</p>
<p>
<span class="dropcap">D</span>epending on how much rain we get Wednesday, for the
first six months of the 2010-11 water year (July 1 to December 31), the rainfall total
for Downtown Los Angeles will likely rank as the fourth or fifth wettest in the 133
years that records have been kept.
</p>
<p>
<span class="dropcap">I</span>n the medium range outlook, the 12z GFS and 12z ECMWF <a href="wxdata1011/sjsu_500cf144hr_122610_12zb.gif" rel="wximage" target="_blank">differ
in how they handle an upper level low</a> that they forecast to develop off the California
coast New Year's morning. The 12z GFS is quite wet New Year's weekend, but it's too
early to put much credence in that forecast. We'll see!
</p>
<p>
<span class="dropcap">M</span>ore information concerning Southern California weather
can be found using our <a href="weatherlinks.htm">WEATHER LINKS</a> page.
</p>
<div class="clearfloat">
</div>
</div>
<img width="0" height="0" src="http://www.sierraphotography.com/wxnotes/aggbug.ashx?id=76d90475-b6b0-458c-ba94-0c2fb6d71b07" />
<br />
<hr />Southern California Weather Notes Copyright 2000-2017 Gary Valle. All Rights Reserved.Los Angeles rainfallprecipitation outlookrecord rainfallweatherhttp://www.sierraphotography.com/wxnotes/Trackback.aspx?guid=90dca7ad-f3ac-4b45-bcd1-1caf85251ac8http://www.sierraphotography.com/wxnotes/pingback.aspxhttp://www.sierraphotography.com/wxnotes/PermaLink,guid,90dca7ad-f3ac-4b45-bcd1-1caf85251ac8.aspxGary Valle

AHPS Precipitation (Percent of Normal)
For 90 Days Ending December 23, 2010 at 4:00 a.m.

After producing phenomenal rainfall totals in Southern
California and snowfall totals in the higher elevations of the Sierra, the Pacific
low and trough responsible for days and days of wet weather has finally moved east.

Some stations recorded more rain in the last 7 days that
would normally be recorded over an entire year. Precipitation amounts over 10 inches
were common, and several stations recorded over 20 inches. Tanbark, in the San Gabriel
Mountains recorded 24.7 inches, NF Matilija in the Ventura Mountains recorded 24.09
inches, and Lytle Creek in the San Bernardino Mountains recorded an astonishing 26.35
inches!

The remarkable amount of rainfall makes December 2010
one of the wettest on record in Southern California. According to preliminary NWS
data Downtown Los Angeles (USC) has recorded 8.52 inches of rain so far this December.
This ranks it as the third wettest December in Los Angeles since recordkeeping began
in 1877, exceeded only by December 1889 (15.8 inches) and December 2004 (8.77 inches).
With additional rain a possibility, December 2010 only needs 0.25 inch to surpass
2004. For more detailed info see "A
Look at the Record-Breaking Week of Rainfall" a PDF from the NWS Los Angeles/Oxnard.

The Sierra recorded gargantuan snowfall totals, with
some of the largest being in the Southern Sierra. In the last week the snow sensor
at Farewell Gap recorded 22.6 inches snow water equivalent, which roughly translates
to 18 feet of snow. This morning California
Cooperative Snow Surveys reports the Southern Section Sierra snowpack at 287%
of normal, and the snowpack overall in the Sierra at 207%! Mammoth Mountain reports
167 inches of snow so far this December, a new record for the period
1968 to date, obliterating the records set in 1971 (139.8 inches) and 2002 (134.4
inches).

As of yesterday Downtown Los Angeles (USC) rainfall was
a whopping 6.88 inches above normal for the water year. That puts us way, way ahead
of what is typical for a La Nina influenced rain season -- at least for a couple of
months.

Update December 24, 2010. Looks like there will be two opportunities before
the end of December for Downtown Los Angeles (USC) to increase its rainfall total
for the month and become the second wettest December since recordkeeping began in
1877. The first chance is Saturday night. For the 24 hour period ending 10:00 a.m.
Sunday, the 09z
SREF puts the probability of more than 0.25 inch of precipitation in the Los Angeles
area at about 70%. The WRF ensembles precipitation forecast for LAX for Saturday night
ranges from a low of about 0.25 inch to a high of about 0.7 inch. The 18z GFS says
the second opportunity will be Wednesday, and forecasts a little under an inch of
rain at LAX. We'll see!

More information concerning Southern California weather
can be found using our WEATHER LINKS page.

Southern California Weather Notes Copyright 2000-2017 Gary Valle. All Rights Reserved.
Southland Records Astronomic Rainfall Totals in Historic 7-Day Rain Event! December 2010 Already One of the Wettest on Record.http://www.sierraphotography.com/wxnotes/PermaLink,guid,90dca7ad-f3ac-4b45-bcd1-1caf85251ac8.aspxhttp://www.sierraphotography.com/wxnotes/SouthlandRecordsAstronomicRainfallTotalsInHistoric7DayRainEventDecember2010AlreadyOneOfTheWettestOnRecord.aspx
Thu, 23 Dec 2010 20:30:24 GMT
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<p align="center">
<a title="AHPS Precipitation (Percent of Normal) for 90 Days Ending December 23, 2010 at 4:00 a.m." href="wxdata1011/AHPSPrecip90DayPON122310_12zb.jpg" rel="wximage"> <img border="0" alt="AHPS Precipitation (Percent of Normal) For 90 Days Ending December 23, 2010 at 4:00 a.m" src="wxdata1011/AHPSPrecip90DayPON122310_12zc.jpg" width="350" height="255" /> </a> <img alt="Click" src="images/click.gif" width="16" height="34" />
<br />
<span class="fontxxsmall">AHPS Precipitation (Percent of Normal)<br />
For 90 Days Ending December 23, 2010 at 4:00 a.m.</span>
</p>
</div>
<p>
<span class="dropcap">A</span>fter producing phenomenal rainfall totals in Southern
California and snowfall totals in the higher elevations of the Sierra, the Pacific
low and trough responsible for days and days of wet weather has finally moved east.
</p>
<p>
<span class="dropcap">S</span>ome stations recorded more rain in the last 7 days that
would normally be recorded over an entire year. Precipitation amounts over 10 inches
were common, and several stations recorded over 20 inches. Tanbark, in the San Gabriel
Mountains recorded 24.7 inches, NF Matilija in the Ventura Mountains recorded 24.09
inches, and Lytle Creek in the San Bernardino Mountains recorded an astonishing 26.35
inches!
</p>
<p>
<span class="dropcap">H</span>ere's are snapshots of provisional <a title="Snapshot of Ventura County Watershed Protection District ALERT Map Viewer 7 Day Precipitation Totals for period ending 12/23/10.&lt;br&gt;(Data is provisional and has not been checked for accuracy.)" href="wxdata1011/VCPWD_7day_Precip_VEN_122310_0645zb.jpg" rel="wximage">7-day
rainfall totals in Ventura County</a> and <a title="Snapshot of Ventura County Watershed Protection District ALERT Map Viewer 7 Day Precipitation Totals for period ending 12/23/10.&lt;br&gt;(Data is provisional and has not been checked for accuracy.)" href="wxdata1011/VCPWD_7day_Precip_LA_122310_0645zb.jpg" rel="wximage">7-day
rainfall totals in Los Angeles County</a> from the <a href="http://www.vcwatershed.org/fws/gmap.html" target="_blank">Ventura
County Watershed Protection District ALERT Map Viewer</a>; and a snapshot of provisional <a title="Snapshot of NWS San Diego Experimental Rainfall Summary Display 7 Day Precipitation Totals for period ending 12/23/10.&lt;br&gt;(Data is provisional and has not been checked for accuracy.)" href="wxdata1011/NWS_7day_Precip_SGX_122310_0645zb.jpg" rel="wximage">7-day
rainfall totals</a> from the <a href="http://www.wrh.noaa.gov/sgx/kml/rrm.php?wfo=sgx" target="_blank">NWS
San Diego's Experimental Rainfall Summary Display</a>. And here are archived copies
of NWS precipitation summaries with preliminary rainfall totals from the <a href="wxdata1011/RRMLOX122310_0419PST.pdf" target="_blank">NWS
Los Angeles/Oxnard</a> and <a href="wxdata1011/RRMSGX122210_1700PST.pdf">NWS San Diego</a> offices.
</p>
<p>
<span class="dropcap">T</span>he remarkable amount of rainfall makes December 2010
one of the wettest on record in Southern California. According to preliminary NWS
data Downtown Los Angeles (USC) has recorded 8.52 inches of rain so far this December.
This ranks it as the third wettest December in Los Angeles since recordkeeping began
in 1877, exceeded only by December 1889 (15.8 inches) and December 2004 (8.77 inches).
With additional rain a possibility, December 2010 only needs 0.25 inch to surpass
2004. For more detailed info see "<a href="wxdata1011/NWSDecRainEvent122310.pdf">A
Look at the Record-Breaking Week of Rainfall</a>" a PDF from the NWS Los Angeles/Oxnard.
</p>
<p>
<span class="dropcap">T</span>he Sierra recorded gargantuan snowfall totals, with
some of the largest being in the Southern Sierra. In the last week the snow sensor
at Farewell Gap recorded 22.6 inches snow water equivalent, which roughly translates
to 18 feet of snow. This morning <a href="http://cdec.water.ca.gov/cgi-progs/reports/DLYSWEQ.20101223" target="_blank">California
Cooperative Snow Surveys reports</a> the Southern Section Sierra snowpack at 287%
of normal, and the snowpack overall in the Sierra at 207%! Mammoth Mountain reports
167 inches of snow so far this December, a new record for the <a href="http://patrol.mammothmountain.com/MMSA-SnowSummary69-09.htm" target="_blank">period
1968 to date</a>, obliterating the records set in 1971 (139.8 inches) and 2002 (134.4
inches).
</p>
<p>
<span class="dropcap">A</span>s of yesterday Downtown Los Angeles (USC) rainfall was
a whopping 6.88 inches above normal for the water year. That puts us way, way ahead
of what is typical for a La Nina influenced rain season -- at least for a couple of
months.
</p>
<p>
<i>Update December 24, 2010</i>. Looks like there will be two opportunities before
the end of December for Downtown Los Angeles (USC) to increase its rainfall total
for the month and become the second wettest December since recordkeeping began in
1877. The first chance is Saturday night. For the 24 hour period ending 10:00 a.m.
Sunday, the <a href="wxdata1011/emc_sref_precip025_57h_122410_09zb.gif" rel="wximage">09z
SREF puts the probability</a> of more than 0.25 inch of precipitation in the Los Angeles
area at about 70%. The WRF ensembles precipitation forecast for LAX for Saturday night
ranges from a low of about 0.25 inch to a high of about 0.7 inch. The 18z GFS says
the second opportunity will be Wednesday, and forecasts a little under an inch of
rain at LAX. We'll see!
</p>
<p>
<span class="dropcap">M</span>ore information concerning Southern California weather
can be found using our <a href="weatherlinks.htm">WEATHER LINKS</a> page.
</p>
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<hr />Southern California Weather Notes Copyright 2000-2017 Gary Valle. All Rights Reserved.La NinaLos Angeles rainfallrecord rainfallSierra snowpackweatherhttp://www.sierraphotography.com/wxnotes/Trackback.aspx?guid=55f32a12-9038-4e4f-af6a-949f40a235bdhttp://www.sierraphotography.com/wxnotes/pingback.aspxhttp://www.sierraphotography.com/wxnotes/PermaLink,guid,55f32a12-9038-4e4f-af6a-949f40a235bd.aspxGary Valle

HPC 5-Day Precipitation Forecast
For the 5 Day Period Ending December 22, 2010 at 4:00 a.m.

If current precipitation forecasts and outlooks validate,
December 2010 could become one of the wettest on record in California, and at the
higher elevations of the Sierra, one of the most snowy. This morning's 5-day
precipitation forecast from the Hydrometeorological Prediction Center, for the
5-day period ending early Wednesday morning, indicates up to 7.9 inches of precipitation
locally, and 14.7 inches (water equivalent) in the Sierra. And additional precipitation
is forecast beyond the 5 day period.

A large Pacific low working in concert with a low west
of Hawaii has established
a tropical connection, and is pumping copious amounts of moisture into California.
This tropical
moisture conveyor belt scenario is currently forecast to continue into next week.
Late Sunday, shortwave impulses dig down into the low and elongate it southwestward,
creating a large longwave trough. This northern part of this trough is forecast to
evolve into another large upper and surface low in the northeastern Pacific. The southern
part of the trough is forecast to develop
a surface low and front that moves into Southern California Tuesday into Wednesday.

It's a little early to put much credence in forecasts
for next week, other than more rain appears likely. The 06z GFS produced astronomic
precipitation totals mid-week -- several inches more than either yesterday afternoon's
00z run (2.75 inches), or this morning's 12z run (4.6 inches). We'll see!

As of yesterday Downtown Los Angeles (USC) rainfall was
0.91 inch below normal for the water year, and much of Southern California was falling
behind in the rainfall department. It looks like by next week we'll be ahead of the
La Nina game again, perhaps way ahead.

More information concerning Southern California weather
can be found using our WEATHER LINKS page.

Southern California Weather Notes Copyright 2000-2017 Gary Valle. All Rights Reserved.
HPC Forecasts Up To 8 Inches Rain Locally, 14 Inches SWE in Sierra, Over Next 5 Days!http://www.sierraphotography.com/wxnotes/PermaLink,guid,55f32a12-9038-4e4f-af6a-949f40a235bd.aspxhttp://www.sierraphotography.com/wxnotes/HPCForecastsUpTo8InchesRainLocally14InchesSWEInSierraOverNext5Days.aspx
Fri, 17 Dec 2010 18:48:15 GMT
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<a title="AHPS Precipitation (Percent of Normal) for 60 Days Ending November 22, 2010 at 4:00 a.m." href="wxdata1011/hpc_5dayqpf121710_1210zb.gif" rel="wximage"> <img border="0" alt="HPC 5-Day Precipitation Forecast For the 5 Day Period Ending December 22, 2010 at 4:00 a.m." src="wxdata1011/hpc_5dayqpf121710_1210zc.gif" width="350" height="262" /> </a> <img alt="Click" src="images/click.gif" width="16" height="34" />
<br />
<span class="fontxxsmall">HPC 5-Day Precipitation Forecast<br />
For the 5 Day Period Ending December 22, 2010 at 4:00 a.m.</span>
</p>
</div>
<p>
<span class="dropcap">I</span>f current precipitation forecasts and outlooks validate,
December 2010 could become one of the wettest on record in California, and at the
higher elevations of the Sierra, one of the most snowy. This morning's <a title="AHPS Precipitation (Percent of Normal) for 60 Days Ending November 22, 2010 at 4:00 a.m." href="wxdata1011/hpc_5dayqpf121710_1210zb.gif" rel="wximage">5-day
precipitation forecast</a> from the Hydrometeorological Prediction Center, for the
5-day period ending early Wednesday morning, indicates up to 7.9 inches of precipitation
locally, and 14.7 inches (water equivalent) in the Sierra. And additional precipitation
is forecast beyond the 5 day period.
</p>
<p>
<span class="dropcap">A</span> large Pacific low working in concert with a low west
of Hawaii has <a href="wxdata1011/uwmad_goes11wv_121710_1500zb.jpg" rel="wximage" target="_blank">established
a tropical connection</a>, and is pumping copious amounts of moisture into California.
This <a href="wxdata1011/GFS_700mb_rh_121710_48hr_12zb.jpg" rel="wximage" target="_blank">tropical
moisture conveyor belt scenario</a> is currently forecast to continue into next week.
Late Sunday, shortwave impulses dig down into the low and elongate it southwestward,
creating a large longwave trough. This northern part of this trough is forecast to
evolve into another large upper and surface low in the northeastern Pacific. The southern
part of the trough is forecast to <a href="wxdata1011/GFS_mslp_121710_126hr_12zb.png" rel="wximage" target="_blank">develop
a surface low and front</a> that moves into Southern California Tuesday into Wednesday.
</p>
<p>
<span class="dropcap">I</span>n the short term, BUFKIT analysis of WRF ensemble data
for Van Nuys shows <a href="wxdata1011/eWRF_precip_121710_12zb.png" rel="wximage" target="_blank">precipitation
totals through early Sunday morning</a> ranging from about 1.0 inch up to about 3.5
inches. <a href="wxdata1011/NAM_precip_121710_12zb.png" rel="wximage" target="_blank">Analysis
of 12z NAM data for Van Nuys</a> produces around 1.8 inches through early Sunday morning
and nearly 5 inches through early Monday morning. The 09z SREF pegs the <a href="wxdata1011/SREF_precipprob_121710_60hr_09zb.png" rel="wximage" target="_blank">probability
of more than 1.0 inch of precipitation</a> in Los Angeles area at around 70%. Precipitable
water values of over 1.0 inch, high relative humidity, and a strong south to southwesterly
inflow of over 30 knots should produce significantly enhanced precipitation on favored
slopes -- generally those with a south to southwest aspect.
</p>
<p>
<span class="dropcap">I</span>t's a little early to put much credence in forecasts
for next week, other than more rain appears likely. The 06z GFS produced astronomic
precipitation totals mid-week -- several inches more than either yesterday afternoon's
00z run (2.75 inches), or this morning's 12z run (4.6 inches). We'll see!
</p>
<p>
<span class="dropcap">A</span>s of yesterday Downtown Los Angeles (USC) rainfall was
0.91 inch below normal for the water year, and much of Southern California was falling
behind in the rainfall department. It looks like by next week we'll be ahead of the
La Nina game again, perhaps way ahead.
</p>
<p>
<span class="dropcap">M</span>ore information concerning Southern California weather
can be found using our <a href="weatherlinks.htm">WEATHER LINKS</a> page.
</p>
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<hr />Southern California Weather Notes Copyright 2000-2017 Gary Valle. All Rights Reserved.climateLa NinaLos Angeles rainfallprecipitation outlookQPF forecastSierra snowpackweather